Book X.

BOOK X.
Questions as to the methods of smelting ores and
of obtaining metals I discussed in Book IX.
Following this, I should explain in what manner the
precious metals are parted from the base metals, or
on the other hand the base metals from the precious 1 .
Frequently two metals, occasionally more than
two, are melted out of one ore, because in
nature generally there is some amount of gold in
silver and in copper, and some silver in gold, copper,
lead, and iron; likewise some copper in gold, silver, lead, and iron, and
some lead in silver; and lastly, some iron in copper 2 . But I will begin with
gold.
Gold is parted from silver, or likewise the latter from the former, whether
it be mixed by nature or by art, by means of aqua valens 3 , and by powders
which consist of almost the same things as this aqua. In order to preserve the
sequence, I will first speak of the ingredients of which this aqua is made, then
of the method of making it, then of the manner in which gold is parted from
silver or silver from gold. Almost all these ingredients contain vitriol or
alum, which, by themselves, but much more when joined with saltpetre, are
powerful to part silver from gold. As to the other things that are added to
them, they cannot individually by their own strength and nature separate
those metals, but joined they are very powerful. Since there are many
combinations, I will set out a few. In the first, the use of which is common
and general, there is one líbra of vitriol and as much salt, added to a third of a
líbra of spring water. The second contains two líbrae of vitriol, one of salt−
petre, and as much spring or river water by weight as will pass away whilst
the vitriol is being reduced to powder by the fire. The third consists of four
líbrae of vitriol, two and a half librae of saltpetre, half a líbra of alum, and one
and a half líbrae of spring water. The fourth consists of two líibrae of vitriol,
as many líbrae of saltpetre, one quarter of a líbra of alum, and three−quarters
of a líbra of spring water. The fifth is composed of one líbra of saltpetre,
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three librae of alum, half a libra of brick dust, and three−quarters of a líbra
of spring water. The sixth consists of four librae of vitriol, three librae of
saltpetre, one of alum, one libra likewise of stones which when thrown into a
fierce furnace are easily liquefied by fire of the third order, and one and a
half librae of spring water. The seventh is made of two librae of vitriol, one
and a half librae of saltpetre, half a libra of alum, and one libra of stones
which when thrown into a glowing furnace are easily liquefied by fire of the
third order, and five−sixths of a líbra of spring water. The eighth is made of
two líbrae of vitriol, the same number of librae of saltpetre, one and a
half librae of alum, one libra of the lees of the aqua which parts gold from
silver; and to each separate líbra a sixth of urine is poured over it. The
ninth contains two líbrae of powder of baked bricks, one libra of vitriol,
likewise one líbra of saltpetre, a handful of salt, and three−quarters of a libra
of spring water. Only the tenth lacks vitriol and alum, but it contains three
librae of saltpetre, two librae of stones which when thrown into a hot furnace
are easily liquefied by fire of the third order, half a libra each of verdigris 4 ,
of stibium, of iron scales and filings, and of asbestos 5 , and one and one−sixth
librae of spring water.
All the vitriol from which the aqua is usually made is first reduced to
powder in the following way. It is thrown into an earthen crucible lined on
the inside with litharge, and heated until it melts; then it is stirred with a
copper wire, and after it has cooled it is pounded to powder. In the same
manner saltpetre melted by the fire is pounded to powder when it has cooled.
Some indeed place alum upon an iron plate, roast it, and make it into powder.
Although all these aquae cleanse gold concentrates or dust from
impurities, yet there are certain compositions which possess singular power.
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The first of these consists of one libra of verdigris and three−quarters of
a líbra of vitriol. For each libra there is poured over it one−sixth of a libra
of spring or river water, as to which, since this pertains to all these com−
pounds, it is sufficient to have mentioned once for all. The second com−
position is made from one líbra of each of the following, artificial orpiment,
vitriol, lime, alum, ash which the dyers of wool use, one quarter of a libra
of verdigris, and one and a half unciae of stibium. The third consists of three
librae of vitriol, one of saltpetre, half a libra of asbestos, and half a libra of
baked bricks. The fourth consists of one libra of saltpetre, one libra of alum,
and half a líbra of sal−ammoniac. 6
The furnace in which aqua valens is made 7 is built of bricks, rectangular,
two feet long and wide, and as many feet high and a half besides. It is
covered with iron plates supported with iron rods; these plates are smeared
on the top with lute, and they have in the centre a round hole, large enough to
hold the earthen vessel in which the glass ampulla is placed, and on each side of
the centre hole are two small round air−holes. The lower part of the furnace,
in order to hold the burning charcoal, has iron plates at the height of a palm,
likewise supported by iron rods. In the middle of the front there is the
mouth, made for the purpose of putting the fire into the furnace; this mouth
is half a foot high and wide, and rounded at the top, and under it is the
draught opening. Into the earthen vessel set over the hole is placed clean
sand a digit deep, and in it the glass ampulla is set as deeply as it is smeared
with lute. The lower quarter is smeared eight or ten times with nearly liquid
lute, each time to the thickness of a blade, and each time it is dried again,
until it has become as thick as the thumb; this kind of lute is well beaten
with an iron rod, and is thoroughly mixed with hair or cotton thread, or with
wool and salt, that it should not crackle. The many things of which the
compounds are made must not fill the ampulla completely, lest when boiling
they rise into the operculum. The operculum is likewise made of glass,
and is closely joined to the ampulla with linen, cemented with wheat flour
and white of egg moistened with water, and then lute free from salt is spread
over that part of it. In a similar way the spout of the operculum is joined
by linen covered with lute to another glass ampulla which receives the distilled
aqua. A kind of thin iron nail or small wooden peg, a little thicker than a
needle, is fixed in this joint, in order that when air seems necessary to the
artificer distilling by this process he can pull it out; this is necessary when
too much of the vapour has been driven into the upper part. The four air−
holes which, as I have said, are on the top of the furnace beside the large
hole on which the ampulla is placed, are likewise covered with lute.
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AFURNACE. BITS ROUND HOLE. CAIR−HOLES. DMOUTH OF THE FURNACE.
EDRAUGHT OPENING UNDER IT. FEARTHENWARE CRUCIBLE. GAMPULLA.
HOPERCULUM. IITS SPOUT. KOTHER AMPULLA. LBASKET IN WHICH THIS IS
USUALLY PLACED LEST IT SHOULD BE BROKEN.
All this preparation having been accomplished in order, and the
ingredients placed in the ampulla, they are gradually heated over burning
charcoal until they begin to exhale vapour and the ampulla is seen to trickle
with moisture. But when this, on account of the rising of the vapour, turns
red, and the aqua distils through the spout of the operculum, then one must
work with the utmost care, lest the drops should fall at a quicker rate than
one for every five movements of the clock or the striking of its bell, and
not slower than one for every ten; for if it falls faster the glasses will be
broken, and if it drops more slowly the work begun cannot be completed
within the definite time, that is within the space of twenty−four hours. To
prevent the first accident, part of the coals are extracted by means of an iron
implement similar to pincers; and in order to prevent the second happening,
small dry pieces of oak are placed upon the coals, and the substances in the
ampulla are heated with a sharper fire, and the air−holes on the furnace
are re−opened if need arise. As soon as the drops are being distilled,
the glass ampulla which receives them is covered with a piece of linen
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moistened with water, in order that the powerful vapour which arises may be
repelled. When the ingredients have been heated and the ampulla in which
they were placed is whitened with moisture, it is heated by a fiercer fire until
all the drops have been distilled 8 . After the furnace has cooled, the aqua is
filtered and poured into a small glass ampulla, and into the same is put half
a drachma of silver 9 , which when dissolved makes the turbid aqua clear.
This is poured into the ampulla containing all the rest of the aqua, and as
soon as the lees have sunk to the bottom the aqua is poured off, removed, and
reserved for use.
Gold is parted from silver by the following method 10 . The alloy, with lead
added to it, is first heated in a cupel until all the lead is exhaled, and eight
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ounces of the alloy contain only five drachmae of copper or at most six, for
if there is more copper in it, the silver separated from the gold soon unites
with it again. Such molten silver containing gold is formed into granules,
being stirred by means of a rod split at the lower end, or else is poured into an
iron mould, and when cooled is made into thin leaves. As the process of
making granules from argentiferous gold demands greater care and diligence than
making them from any other metals, I will now explain the method briefly. The
alloy is first placed in a crucible, which is then covered with a lid and placed
in another earthen crucible containing a few ashes. Then they are placed
in the furnace, and after they are surrounded by charcoal, the fire is blown
by the blast of a bellows, and lest the charcoal fall away it is surrounded
by stones or bricks. Soon afterward charcoal is thrown over the upper
crucible and covered with live coals; these again are covered with charcoal,
so that the crucible is surrounded and covered on all sides with it. It
is necessary to heat the crucibles with charcoal for the space of half an hour or
a little longer, and to provide that there is no deficiency of charcoal, lest the
alloy become chilled; after this the air is blown in through the nozzle of the
bellows, that the gold may begin to melt. Soon afterward it is turned
round, and a test is quickly taken to see whether it be melted, and if it is
melted, fluxes are thrown into it; it is advisable to cover up the crucible
again closely that the contents may not be exhaled. The contents are heated
together for as long as it would take to walk fifteen paces, and then the
crucible is seized with tongs and the gold is emptied into an oblong vessel
containing very cold water, by pouring it slowly from a height so that the
granules will not be too big; in proportion as they are lighter, more fine
and more irregular, the better they are, therefore the water is frequently
stirred with a rod split into four parts from the lower end to the middle.
The leaves are cut into small pieces, and they or the silver granules are
put into a glass ampulla, and the aqua is poured over them to a height of a
digit above the silver. The ampulla is covered with a bladder or with waxed
linen, lest the contents exhale. Then it is heated until the silver is dissolved,
the indication of which is the bubbling of the aqua. The gold remains in the
bottom, of a blackish colour, and the silver mixed with the aqua floats above.
Some pour the latter into a copper bowl and pour into it cold water, which
immediately congeals the silver; this they take out and dry, having poured
off the aqua 11 . They heat the dried silver in an earthenware crucible until
it melts, and when it is melted they pour it into an iron mould.
The gold which remains in the ampulla they wash with warm water,
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filter, dry, and heat in a crucible with a little chrysocolla which is called
borax, and when it is melted they likewise pour it into an iron mould.
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Some workers, into an ampulla which contains gold and silver and the
aqua which separates them, pour two or three times as much of this aqua
valens warmed, and into the same ampulla or into a dish into which all is
poured, throw fine leaves of black lead and copper; by this means the gold
adheres to the lead and the silver to the copper, and separately the lead
from the gold, and separately the copper from the silver, are parted in a
cupel. But no method is approved by us which loses the aqua used to part
gold from silver, for it might be used again 12 .
A glass ampulla, which bulges up inside at the bottom like a cone, is
covered on the lower part of the outside with lute in the way explained above,
and into it is put silver bullion weighing three and a half Roman librae. The
aqua which parts the one from the other is poured into it, and the ampulla is
placed in sand contained in an earthen vessel, or in a box, that it may be
warmed with a gentle fire. Lest the aqua should be exhaled, the top of the
ampulla is plastered on all sides with lute, and it is covered with a glass
operculum, under whose spout is placed another ampulla which receives the
distilled drops; this receiver is likewise arranged in a box containing sand.
When the contents are heated it reddens, but when the redness no
longer appears to increase, it is taken out of the vessel or box and shaken;
by this motion the aqua becomes heated again and grows red; if this is
done two or three times before other aqua is added to it, the operation is sooner
concluded, and much less aqua is consumed. When the first charge has all
been distilled, as much silver as at first is again put into the ampulla, for if
too much were put in at once, the gold would be parted from it with difficulty.
Then the second aqua is poured in, but it is warmed in order that it and the
ampulla may be of equal temperature, so that the latter may not be cracked
by the cold; also if a cold wind blows on it, it is apt to crack. Then the third
aqua is poured in, and also if circumstances require it, the fourth, that is to
say more aqua and again more is poured in until the gold assumes the colour
of burned brick. The artificer keeps in hand two aquae, one of which is
stronger than the other; the stronger is used at first, then the less strong,
then at the last again the stronger. When the gold becomes of a reddish
yellow colour, spring water is poured in and heated until it boils. The gold is
washed four times and then heated in the crucible until it melts. The water
with which it was washed is put back, for there is a little silver in it; for
this reason it is poured into an ampulla and heated, and the drops first distilled
are received by one ampulla, while those which come later, that is to say
when the operculum begins to get red, fall into another. This latter aqua is
useful for testing the gold, the former for washing it; the former may also
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be poured over the ingredients from which the aqua valens is made.
The aqua that was first distilled, which contains the silver, is poured into
an ampulla wide at the base, the top of which is also smeared with lute and
covered by an operculum, and is then boiled as before in order that it may be
separated from the silver. If there be so much aqua that (when boiled) it
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AAMPULLAE ARRANGED IN THE VESSELS. BAN AMPULLA STANDING UPRIGHT BETWEEN
IRON RODS. CAMPULLAE PLACED IN THE SAND WHICH IS CONTAINED IN A BOX, THE
SPOUTS OF WHICH REACH FROM THE OPERCULA INTO AMPULLAE PLACED UNDER THEM.
DAMPULLAE LIKEWISE PLACED IN SAND WHICH IS CONTAINED IN A BOX, OF WHICH THE
SPOUT FROM THE OPERCULA EXTENDS CROSSWISE INTO AMPULLAE PLACED UNDER THEM.
EOTHER AMPULLAE RECEIVING THE DISTILLED aqua AND LIKEWISE ARRANGED IN SAND
CONTAINED IN THE LOWER BOXES. FIRON TRIPOD, IN WHICH THE AMPULLA IS USUALLY
PLACED WHEN THERE ARE NOT MANY PARTICLES OF GOLD TO BE PARTED FROM THE
SILVER.
GVESSEL.
rises into the operculum, there is put into the ampulla one lozenge or two;
these are made of soap, cut into small pieces and mixed together with
powdered argol, and then heated in a pot over a gentle fire; or else the
contents are stirred with a hazel twig split at the bottom, and in both cases
the aqua effervesces, and soon after again settles. When the powerful vapour
appears, the aqua gives off a kind of oil, and the operculum becomes red. But,
lest the vapours should escape from the ampulla and the operculum in that
part where their mouths communicate, they are entirely sealed all round.
The aqua is boiled continually over a fiercer fire, and enough charcoal must be
put into the furnace so that the live coals touch the vessel. The ampulla is
taken out as soon as all the aqua has been distilled, and the silver, which is dried
by the heat of the fire, alone remains in it; the silver is shaken out and put
in an earthenware crucible, and heated until it melts. The molten glass is
extracted with an iron rod curved at the lower end, and the silver is made
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into cakes. The glass extracted from the crucible is ground to powder, and
to this are added litharge, argol, glass−galls, and saltpetre, and they are
melted in an earthen crucible. The button that settles is transferred to the
cupel and re−melted.
If the silver was not sufficiently dried by the heat of the fire, that which
is contained in the upper part of the ampulla will appear black; this when
melted will be consumed. When the lute, which was smeared round the
lower part of the ampulla, has been removed, it is placed in the crucible and
is re−melted, until at last there is no more appearance of black 13 .
If to the first aqua the other which contains silver is to be added, it
must be poured in before the powerful vapours appear, and the aqua gives off
the oily substance, and the operculum becomes red; for he who pours in the
aqua after the vapour appears causes a loss, because the aqua generally spurts
out and the glass breaks. If the ampulla breaks when the gold is being parted
from the silver or the silver from the aqua, the aqua will be absorbed by the
sand or the lute or the bricks, whereupon, without any delay, the red hot coals
should be taken out of the furnace and the fire extinguished. The sand and
bricks after being crushed should be thrown into a copper vessel, warm water.
should be poured over them, and they should be put aside for the space of
twelve hours; afterward the water should be strained through a canvas, and
the canvas, since it contains silver, should be dried by the heat of the sun or
the fire, and then placed in an earthen crucible and heated until the silver
melts, this being poured out into an iron mould. The strained water should
be poured into an ampulla and separated from the silver, of which it contains
a minute portion; the sand should be mixed with litharge, glass−galls,
argol, saltpetre, and salt, and heated in an earthen crucible. The button
which settles at the bottom should be transferred to a cupel, and should
be re−melted, in order that the lead may be separated from the silver. The
lute, with lead added, should be heated in an earthen crucible, then
re−melted in a cupel.
We also separate silver from gold by the same method when we assay
them. For this purpose the alloy is first rubbed against a touchstone, in
order to learn what proportion of silver there is in it; then as much silver
as is necessary is added to the argentiferous gold, in a bes of which there
must be less than a semí−uncía or a semí−uncía and a sicilicus 14 of copper.
After lead has been added, it is melted in a cupel until the lead and the
copper have exhaled, then the alloy of gold with silver is flattened out, and
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little tubes are made of the leaves; these are put into a glass ampulla,
and strong aqua is poured over them two or three times. The tubes after
this are absolutely pure, with the exception of only a quarter of a siliqua,
which is silver; for only this much silver remains in eight uncíae of gold 15 .
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As great expense is incurred in parting the metals by the methods that
I have explained, as night vigils are necessary when aqua valens is made,
and as generally much labour and great pains have to be expended on this
matter, other methods for parting have been invented by clever men, which
are less costly, less laborious, and in which there is less loss if through care−
lessness an error is made. There are three methods, the first performed with
sulphur, the second with antimony, the third by means of some compound
which consists of these or other ingredients.
In the first method, 16 the silver containing some gold is melted in a
crucible and made into granules. For every libra of granules, there is taken
a sixth of a libra and a sícilicus of sulphur (not exposed to the fire); this,
when crushed, is sprinkled over the moistened granules, and then they are put
into a new carthen pot of the capacity of four sextarií, or into several of them
if there is an abundance of granules. The pot, having been filled, is covered
with an earthen lid and smeared over, and placed within a circle of fire set one
and a half feet distant from the pot on all sides, in order that the sulphur
added to the silver should not be distilled when melted. The pot is opened,
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APOT. BCIRCULAR FIRE. CCRUCIBLES. DTHEIR LIDS. ELID OF THE POT.
FFURNACE. GIRON ROD.
the black−coloured granules are taken out, and afterward thirty−three librae
of these granules are placed in an earthen crucible, if it has such capacity.
For every líbra of silver granules, weighed before they were sprinkled with
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sulphur, there is weighed out also a sixth of a líbra and a sicílícus of
copper, if each libra consists either of three−quarters of a líbra of silver and
a quarter of a libra of copper, or of three−quarters of a libra and a
semí−uncia of silver and a sixth of a libra and a semí−uncía of copper. If,
however, the silver contains five−sixths of a libra of silver and a sixth of a
líbra of copper, or five−sixths of a líbra and a semí−uncía of silver and an uncía
and a half of copper, then there are weighed out a quarter of a libra of copper
granules. If a líbra contains eleven−twelfths of a líbra of silver and one uncía
of copper, or eleven−twelfths and a semí−uncía of silver and a semí−uncia of
copper, then are weighed out a quarter of a libra and a semi−uncia and a
sícílicus of copper granules. Lastly, if there is only pure silver, then as much
as a third of a líbra and a semí−uncía of copper granules are added. Half
of these copper granules are added soon afterward to the black−coloured
silver granules. The crucible should be tightly covered and smeared over
with lute, and placed in a furnace, into which the air is drawn through the
draught−holes. As soon as the silver is melted, the crucible is opened, and
there is placed in it a heaped ladleful more of granulated copper, and also
a heaped ladleful of a powder which consists of equal parts of litharge, of
granulated lead, of salt, and of glass−galls; then the crucible is again covered
with the lid. When the copper granules are melted, more are put in, together
with the powder, until all have been put in.
A little of the regulus is taken from the crucible, but not from the gold
lump which has settled at the bottom, and a drachma of it is put into each of
the cupels, which contain an uncia of molten lead; there should be many
of these cupels. In this way half a drachma of silver is made. As soon as
the lead and copper have been separated from the silver, a third of it is
thrown into a glass ampulla, and aqua valens is poured over it. By this
method is shown whether the sulphur has parted all the gold from the silver,
or not. If one wishes to know the size of the gold lump which has settled
at the bottom of the crucible, an iron rod moistened with water is covered
with chalk, and when the rod is dry it is pushed down straight into the
crucible, and the rod remains bright to the height of the gold lump; the
remaining part of the rod is coloured black by the regulus, which adheres to
the rod if it is not quickly removed.
If when the rod has been extracted the gold is observed to be
satisfactorily parted from the silver, the regulus is poured out, the gold
button is taken out of the crucible, and in some clean place the regulus is
chipped off from it, although it usually flies apart. The lump itself is reduced
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to granules, and for every libra of this gold they weigh out a quarter of a libra
each of crushed sulphur and of granular copper, and all are placed together
in an earthen crucible, not into a pot. When they are melted, in order that
the gold may more quickly settle at the bottom, the powder which I have
mentioned is added.
Although minute particles of gold appear to scintillate in the regulus
of copper and silver, yet if all that are in a libra do not weigh as much as a
single sesterce, then the sulphur has satisfactorily parted the gold from the
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silver; but if it should weigh a sesterce or more, then the regulus is thrown
back again into the earthen crucible, and it is not advantageous to add sulphur,
but only a little copper and powder, by which method a gold lump is again
made to settle at the bottom; and this one is added to the other button which
is not rich in gold.
When gold is parted from sixty−six líbrae of silver, the silver, copper,
and sulphur regulus weighs one hundred and thirty−two librae. To separate
the copper from the silver we require five hundred líbrae of lead, more or
less, with which the regulus is melted in the second furnace. In this
manner litharge and hearth−lead are made, which are re−smelted in the first
furnace. The cakes that are made from these are placed in the third furnace,
so that the lead may be separated from the copper and used again, for it
contains very little silver. The crucibles and their covers are crushed, washed,
and the sediment is melted together with litharge and hearth−lead.
Those who wish to separate all the silver from the gold by this method
leave one part of gold to three of silver, and then reduce the alloy to
granules. Then they place it in an ampulla, and by pouring aqua valens over
it, part the gold from the silver, which process I explained in Book VII.
If sulphur from the lye with which sal artíficiosus is made, is strong
enough to float an egg thrown into it, and is boiled until it no longer emits
fumes, and melts when placed upon glowing coals, then, if such sulphur is
thrown into the melted silver, it parts the gold from it.
Silver is also parted from gold by means of stíbíum 17 . If in a bes of
gold there are seven, or six, or five double sextulae of silver, then three parts
of stibium are added to one part of gold; but in order that the stibium should
not consume the gold, it is melted with copper in a red hot earthern crucible.
If the gold contains some portion of copper, then to eight unciae of stibium
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a sicilicus of copper is added; and if it contains no copper, then half an
uncia, because copper must be added to stibium in order to part gold from
silver. The gold is first placed in a red hot earthen crucible, and when
melted it swells, and a little stibium is added to it lest it run over; in a
short space of time, when this has melted, it likewise again swells, and
when this occurs it is advisable to put in all the remainder of the stibium,
and to cover the crucible with a lid, and then to heat the mixture for the
time required to walk thirty−five paces. Then it is at once poured out into
an iron pot, wide at the top and narrow at the bottom, which was first
heated and smeared over with tallow or wax, and set on an iron or wooden
block. It is shaken violently, and by this agitation the gold lump settles
to the bottom, and when the pot has cooled it is tapped loose, and is again
melted four times in the same way. But each time a less weight of stibium
is added to the gold, until finally only twice as much stibium is added as
there is gold, or a little more; then the gold lump is melted in a cupel. The
stibium is melted again three or four times in an earthen crucible, and each
time a gold lump settles, so that there are three or four gold lumps, and
these are all melted together in a cupel.
To two líbrae and a half of such stíbíum are added two librae of argol
and one libra of glass−galls, and they are melted in an earthen crucible,
where a lump likewise settles at the bottom; this lump is melted in the
cupel. Finally, the stibium with a little lead added, is melted in the cupel,
in which, after all the rest has been consumed by the fire, the silver alone
remains. If the stíbium is not first melted in an earthen crucible with argol
and glass−galls, before it is melted in the cupel, part of the silver is consumed,
and is absorbed by the ash and powder of which the cupel is made.
The crucible in which the gold and silver alloy are melted with stíbíum,
and also the cupel, are placed in a furnace, which is usually of the kind
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AFURNACE IN WHICH THE AIR IS DRAWN IN THROUGH HOLES. BGOLDSMITH' S FORGE.
CEARTHEN CRUCIBLES. DIRON POTS. EBLOCK.
in which the air is drawn in through holes; or else they are placed in a gold−
smith' s forge.
Just as aqua valens poured over silver, from which the sulphur has
parted the gold, shows us whether all has been separated or whether
particles of gold remain in the silver; so do certain ingredients, if placed in
the pot or crucible "alternately" with the gold, from which the silver has
been parted by stibíum, and heated, show us whether all have been
separated or not.
We use cements 18 when, without stíbíum, we part silver or copper or both
so ingeniously and admirably from gold. There are various cements. Some
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consist of half a libra of brick dust, a quarter of a libra of salt, an uncía of salt−
petre, half an uncia of sal−ammoniac, and half an uncia of rock salt. The bricks
or tiles from which the dust is made must be composed of fatty clays, free from
sand, grit, and small stones, and must be moderately burnt and very old.
Another cement is made of a bes of brick dust, a third of rock salt, an
uncia of saltpetre, and half an uncia of refined salt. Another cement is made
of a bes of brick dust, a quarter of refined salt, one and a half unciae of
saltpetre, an uncia of sal−ammoniac, and half an uncia of rock salt. Another
has one libra of brick dust, and half a libra of rock salt, to which some add a
sixth of a libra and a sicilicus of vitriol. Another is made of half a libra of
brick dust, a third of a libra of rock salt, an uncía and a half of vitriol, and
one uncia of saltpetre. Another consists of a bes of brick dust, a third of
refined salt, a sixth of white vitriol 19 , half an uncia of verdigris, and likewise
half an uncia of saltpetre. Another is made of one and a third librae of brick
dust, a bes of rock salt, a sixth of a libra and half an uncía of sal−ammoniac,
a sixth and half an uncia of vitriol, and a sixth of saltpetre. Another contains
a libra of brick dust, a third of refined salt, and one and a half uncíae of vitriol.
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Those ingredients above are peculiar to each cement, but what follows
is common to all. Each of the ingredients is first separately crushed to
powder; the bricks are placed on a hard rock or marble, and crushed with an
iron implement; the other things are crushed in a mortar with a pestle;
each is separately passed through a sieve. Then they are all mixed together,
and are moistened with vinegar in which a little sal−ammoniac has been
dissolved, if the cement does not contain any. But some workers, however,
prefer to moisten the gold granules or gold−leaf instead.
The cement should be placed, alternately with the gold, in new and clean
pots in which no water has ever been poured. In the bottom the cement is
levelled with an iron implement, and afterward the gold granules or leaves
are placed one against the other, so that they may touch it on all sides; then,
again, a handful of the cement, or more if the pots are large, is thrown in and
levelled with an iron implement; the granules and leaves are laid over this
in the same manner, and this is repeated until the pot is filled. Then it is
covered with a lid, and the place where they join is smeared over with
artificial lute, and when this is dry the pots are placed in the furnace.
The furnace has three chambers, the lowest of which is a foot high; into
this lowest chamber the air penetrates through an opening, and into it the
AFURNACE. BPOT. CLID. DAIR−HOLES.
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ashes fall from the burnt wood, which is supported by iron rods, arranged to
form a grating. The middle chamber is two feet high, and the wood is pushed
in through its mouth. The wood ought to be oak, holmoak, or turkey−oak,
for from these the slow and lasting fire is made which is necessary for this
operation. The upper chamber is open at the top so that the pots, for which
it has the depth, may be put into it; the floor of this chamber consists of iron
rods, so strong that they may bear the weight of the pots and the heat of the
fire; they are sufficiently far apart that the fire may penetrate well and may
heat the pots. The pots are narrow at the bottom, so that the fire entering
into the space between them may heat them; at the top the pots are wide,
so that they may touch and hold back the heat of the fire. The upper part
of the furnace is closed in with bricks not very thick, or with tiles and lute,
and two or three air−holes are left, through which the fumes and flames may
escape.
The gold granules or leaves and the cement, alternately placed in the pots,
are heated by a gentle fire, gradually increasing for twenty−four hours, if the
furnace was heated for two hours before the full pots were stood in it, and if
this was not done, then for twenty−six hours. The fire should be increased
in such a manner that the pieces of gold and the cement, in which is the
potency to separate the silver and copper from the gold, may not melt, for in
this case the labour and cost will be spent in vain; therefore, it is ample to
have the fire hot enough that the pots always remain red. After so many
hours all the burning wood should be drawn out of the furnace. Then the
refractory bricks or tiles are removed from the top of the furnace, and the
glowing pots are taken out with the tongs. The lids are removed, and
if there is time it is well to allow the gold to cool by itself, for then there is
less loss; but if time cannot be spared for that operation, the pieces of gold
are immediately placed separately into a wooden or bronze vessel of water
and gradually quenched, lest the cement which absorbs the silver should
exhale it. The pieces of gold, and the cement adhering to them, when cooled
or quenched, are rolled with a little mallet so as to crush the lumps and free
the gold from the cement. Then they are sifted by a fine sieve, which is
placed over a bronze vessel; in this manner the cement containing the
silver or the copper or both, falls from the sieve into the bronze vessel, and the
gold granules or leaves remain on it. The gold is placed in a vessel and
again rolled with the little mallet, so that it may be cleansed from the cement
which absorbs silver and copper.
The particles of cement, which have dropped through the holes of the
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sieve into the bronze vessel, are washed in a bowl, over a wooden tub, being
shaken about with the hands, so that the minute particles of gold which have
fallen through the sieve may be separated. These are again washed in a
little vessel, with warm water, and scrubbed with a piece of wood or a twig
broom, that the moistened cement may be detached. Afterward all the gold
is again washed with warm water, and collected with a bristle brush, and should
be washed in a copper full of holes, under which is placed a little vessel.
Then it is necessary to put the gold on an iron plate, under which is a vessel,
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and to wash it with warm water. Finally, it is placed in a bowl, and, when
dry, the granules or leaves are rubbed against a touchstone at the same time
as a touch−needle, and considered carefully as to whether they be pure or
alloyed. If they are not pure enough, the granules or the leaves, together
with the cement which attracts silver and copper, are arranged alternately
in layers in the same manner, and again heated; this is done as often as is
necessary, but the last time it is heated as many hours as are required to
cleanse the gold.
Some people add another cement to the granules or leaves. This cement
lacks the ingredients of metalliferous origin, such as verdigris and vitriol, for
if these are in the cement, the gold usually takes up a little of the base metal;
or if it does not do this, it is stained by them. For this reason some very
rightly never make use of cements containing these things, because brick
dust and salt alone, especially rock salt, are able to extract all the silver and
copper from the gold and to attract it to themselves.
It is not necessary for coiners to make absolutely pure gold, but to heat
it only until such a fineness is obtained as is needed for the gold money which
they are coining.
The gold is heated, and when it shows the necessary golden yellow colour
and is wholly pure, it is melted and made into bars, in which case they are
either prepared by the coiners with chrysocolla, which is called by the Moors
borax, or are prepared with salt of lye made from the ashes of ivy or of
other salty herbs.
The cement which has absorbed silver or copper, after water has been
poured over it, is dried and crushed, and when mixed with hearth−lead and
de−silverized lead, is smelted in the blast furnace. The alloy of silver and
lead, or of silver and copper and lead, which flows out, is again melted in the
cupellation furnace, in order that the lead and copper may be separated from
the silver. The silver is finally thoroughly purified in the refining furnace,
and in this practical manner there is no silver lost, or only a minute quantity.
There are besides this, certain other cements 20 which part gold from
silver, composed of sulphur, stibium and other ingredients. One of these
compounds consists of half an uncía of vitriol dried by the heat of the fire
and reduced to powder, a sixth of refined salt, a third of stibium, half a libra
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of prepared sulphur (not exposed to the fire), one sicilicus of glass, likewise
one sícilicus of saltpetre, and a drachma of sal−ammoniac. 21 The sulphur
is prepared as follows: it is first crushed to powder, then it is heated
for six hours in sharp vinegar, and finally poured into a vessel and washed
with warm water; then that which settles at the bottom of the vessel is
dried. To refine the salt it is placed in river water and boiled, and again
evaporated. The second compound contains one libra of sulphur (not exposed
to fire) and two librae of refined salt. The third compound is made from one
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libra of sulphur (not exposed to the fire), half a líbra of refined salt, a quarter of
a líbra of sal−ammoniac, and one uncía of red−lead. The fourth compound
consists of one líbra each of refined salt, sulphur (not exposed to the fire) and
argol, and half a libra of chrysocolla which the Moors call borax. The fifth
compound has equal proportions of sulphur (not exposed to the fire), sal−
ammoniac, saltpetre, and verdigris.
The silver which contains some portion of gold is first melted with
lead in an earthen crucible, and they are heated together until the silver
exhales the lead. If there was a libra of silver, there must be six drachmae of
lead. Then the silver is sprinkled with two uncíae of that powdered com−
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pound and is stirred; afterward it is poured into another crucible, first
warmed and lined with tallow, and then violently shaken. The rest is per−
formed according to the process I have already explained.
Gold may be parted without injury from silver goblets and from other
gilt vessels and articles 22 , by means of a powder, which consists of one part of
sal−ammoniac and half a part of sulphur. The gilt goblet or other article
is smeared with oil, and the powder is dusted on; the article is seized in the
hand, or with tongs, and is carried to the fire and sharply tapped, and by this
means the gold falls into water in vessels placed underneath, while the
goblet remains uninjured.
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Gold is also parted from silver on gilt articles by means of quicksilver.
This is poured into an earthen crucible, and so warmed by the fire that the
finger can bear the heat when dipped into it; the silver−gilt objects are
placed in it, and when the quicksilver adheres to them they are taken out
and placed on a dish, into which, when cooled, the gold falls, together with the
quicksilver. Again and frequently the same silver−gilt object is placed in
heated quicksilver, and the same process is continued until at last no
more gold is visible on the object; then the object is placed in the fire, and
the quicksilver which adheres to it is exhaled. Then the artificer takes a hare' s
foot, and brushes up into a dish the quicksilver and the gold which have
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fallen together from the silver article, and puts them into a cloth made of woven
cotton or into a soft leather; the quicksilver is squeezed through one or the
other into another dish. 23 The gold remains in the cloth or the leather, and
when collected is placed in a piece of charcoal hollowed out, and is heated
until it melts, and a little button is made from it. This button is heated with
a little stíbíum in an earthen crucible and poured out into another little
vessel, by which method the gold settles at the bottom, and the stíbíum is
seen to be on the top; then the work is completed. Finally, the gold
button is put in a hollowed−out brick and placed in the fire, and by this
method the gold is made pure. By means of the above methods gold is parted
from silver and also silver from gold.
Now I will explain the methods used to separate copper from gold 24 .
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The salt which we call sal−artíficíosus, 25 is made from a líbra each of vitriol,
alum, saltpetre, and sulphur not exposed to the fire, and half a líbra of sal−
ammoniac; these ingredients when crushed are heated with one part of lye made
from the ashes used by wool dyers, one part of unslaked lime, and four
parts of beech ashes. The ingredients are boiled in the lye until the whole
has been dissolved. Then it is immediately dried and kept in a hot place,
lest it turn into oil; and afterward when crushed, a libra of lead−ash is mixed
with it. With each líbra of this powdered compound one and a half uncíae
of the copper is gradually sprinkled into a hot crucible, and it is stirred
rapidly and frequently with an iron rod. When the crucible has cooled and
been broken up, the button of gold is found.
The second method for parting is the following. Two líbrae of sulphur
not exposed to the fire, and four líbrae of refined salt are crushed and mixed;
a sixth of a libra and half an uncía of this powder is added to a bes of granules
made of lead, and twice as much copper containing gold; they are heated
together in an earthen crucible until they melt. When cooled, the button is
taken out and purged of slag. From this button they again make granules,
to a third of a libra of which is added half a líbra of that powder of which I
have spoken, and they are placed in alternate layers in the crucible; it is
well to cover the crucible and to seal it up, and afterward it is heated over a
gentle fire until the granules melt. Soon afterward, the crucible is taken off
the fire, and when it is cool the button is extracted. From this, when purified
and again melted down, the third granules are made, to which, if they weigh
a sixth of a líbra, is added one half an uncia and a sícílicus of the powder,
and they are heated in the same manner, and the button of gold settles at the
bottom of the crucible.
The third method is as follows. From time to time small pieces of
sulphur, enveloped in or mixed with wax, are dropped into six líbrae of the
molten copper, and consumed; the sulphur weighs half an uncia and a
sícílícus . Then one and a half sicílici of powdered saltpetre are dropped
into the same copper and likewise consumed; then again half an uncía and a
sícílícus of sulphur enveloped in wax; afterward one and a half sícílící of
lead−ash enveloped in wax, or of minium made from red−lead. Then imme−
diately the copper is taken out, and to the gold button, which is now mixed
with only a little copper, they add stibíum to dcuble the amount of the button;
these are heated together until the stibíum is driven off; then the button,
together with lead of half the weight of the button, are heated in a cupel.
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Finally, the gold is taken out of this and quenched, and if there is a
blackish colour settled in it, it is melted with a little of the chrysocolla
which the Moors call borax; if too pale, it is melted with stibium, and
acquires its own golden−yellow colour. There are some who take out the
molten copper with an iron ladle and pour it into another crucible, whose
aperture is sealed up with lute, and they place it over glowing charcoal,
and when they have thrown in the powders of which I have spoken, they
stir the whole mass rapidly with an iron rod, and thus separate the gold
from the copper; the former settles at the bottom of the crucible, the latter
floats on the top. Then the aperture of the crucible is opened with the
red−hot tongs, and the copper runs out. The gold which remains is re−heated
with stibium, and when this is exhaled the gold is heated for the third time
in a cupel with a fourth part of lead, and then quenched.
The fourth method is to melt one and a third librae of the copper
with a sixth of a libra of lead, and to pour it into another crucible smeared on
the inside with tallow or gypsum; and to this is added a powder consisting of
half an uncia each of prepared sulphur, verdigris, and saltpetre, and an uncia
and a half of sal coctus. The fifth method consists of placing in a crucible
one libra of the copper and two librae of granulated lead, with one and a half
unciae of sal−artificíosus; they are at first heated over a gentle fire and then
over a fiercer one. The sixth method consists in heating together a bes of
the copper and one−sixth of a libra each of sulphur, salt, and stibium. The
seventh method consists of heating together a bes of the copper and one−sixth
each of iron scales and filings, salt, stibium, and glass−galls. The eighth
method consists of heating together one libra of the copper, one and a half
librae of sulphur, half a libra of verdigris, and a libra of refined salt. The
ninth method consists of placing in one libra of the molten copper as
much pounded sulphur, not exposed to the fire, and of stirring it rapidly
with an iron rod; the lump is ground to powder, into which quicksilver
is poured, and this attracts to itself the gold.
Gilded copper articles are moistened with water and placed on the fire,
and when they are glowing they are quenched with cold water, and the gold
is scraped off with a brass rod. By these practical methods gold is separated
from copper.
Either copper or lead is separated from silver by the methods which I
will now explain. 26 This is carried on in a building near by the works, or
in the works in which the gold or silver ores or alloys are smelted. The
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middle wall of such a building is twenty−one feet long and fifteen feet high, and
from this a front wall is distant fifteen feet toward the river; the rear wall
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is nineteen feet distant, and both these walls are thirty−six feet long and
fourteen feet high; a transverse wall extends from the end of the front wall to
the end of the rear wall; then fifteen feet back a second transverse wall
is built out from the front wall to the end of the middle wall. In that space
which is between those two transverse walls are set up the stamps, by means
of which the ores and the necessary ingredients for smelting are broken up.
From the further end of the front wall, a third transverse wall leads to the
other end of the middle wall, and from the same to the end of the rear wall.
The space between the second and third transverse walls, and between the
rear and middle long walls, contains the cupellation furnace, in which lead
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640
is separated from gold or silver. The vertical wall of its chimney is
erected upon the middle wall, and the sloping chimney−wall rests on the
beams which extend from the second transverse wall to the third; these are
so located that they are at a distance of thirteen feet from the middle long
wall and four from the rear wall, and they are two feet wide and thick.
From the ground up to the roof−beams is twelve feet, and lest the sloping
chimney−wall should fall down, it is partly supported by means of many
iron rods, and partly by means of a few tie−beams covered with lute, which
extend from the small beams of the sloping chimney−wall to the beams of the
vertical chimney−wall. The rear roof is arranged in the same way as the roof
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of the works in which ore is smelted. In the space between the middle and
the front long walls and between the second 27 and the third transverse walls are
the bellows, the machinery for depressing and the instrument for raising them.
A drum on the axle of a water−wheel has rundles which turn the toothed
drum of an axle, whose long cams depress the levers of the bellows, and also
another toothed drum on an axle, whose cams raise the tappets of the stamps,
but in the opposite direction. So that if the cams which depress the levers
of the bellows turn from north to south, the cams of the stamps turn from
south to north.
Lead is separated from gold or silver in a cupellation furnace, of
which the structure consists of rectangular stones, of two interior walls of which
the one intersects the other transversely, of a round sole, and of a dome. Its
crucible is made from powder of earth and ash; but I will first speak of the
structure and also of the rectangular stones. A circular wall is built four
feet and three palms high, and one foot thick; from the height of two feet
and three palms from the bottom, the upper part of the interior is cut away
to the width of one palm, so that the stone sole may rest upon it. There are
usually as many as fourteen stones; on the outside they are a foot and a
palm wide, and on the inside narrower, because the inner circle is much
smaller than the outer; if the stones are wider, fewer are required, if
narrower more; they are sunk into the earth to a depth of a foot and a palm.
At the top each one is joined to the next by an iron staple, the points of
which are embedded in holes, and into each hole is poured molten lead. This
stone structure has six air−holes near the ground, at a height of a foot above
the ground; they are two feet and a palm from the bottom of the stones;
each of these air−holes is in two stones, and is two palms high, and a palm and
three digits wide. One of them is on the right side, between the wall which
protects the main wall from the fire, and the channel through which the
litharge flows out of the furnace crucible; the other five air−holes are
distributed all round at equal distances apart; through these escapes the
moisture which the earth exhales when heated, and if it were not for these
openings the crucible would absorb the moisture and be damaged. In such a
case a lump would be raised, like that which a mole throws up from the earth,
and the ash would float on the top, and the crucible would absorb the silver−lead
alloy; there are some who, because of this, make the rear part of the structure
entirely open. The two inner walls, of which one intersects the other, are
built of bricks, and are a brick in thickness. There are four air−holes in
these, one in each part, which are about one digit' s breadth higher and wider
than the others. Into the four compartments is thrown a wheelbarrowful
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of slag, and over this is placed a large wicker basket full of charcoal dust.
These walls extend a cubit above the ground, and on these, and on the ledge
cut in the rectangular stones, is placed the stone sole; this sole is a palm and
three digits thick, and on all sides touches the rectangular stones; if there
are any cracks in it they are filled up with fragments of stone or brick. The
front part of the sole is sloped so that a channel can be made, through which
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the litharge flows out. Copper plates are placed on this part of the sole−stone
so that the silver−lead or other alloy may be more rapidly heated.
A dome which has the shape of half a sphere covers the crucible. It con−
sists of iron bands and of bars and of a lid. There are three bands, each about
a palm wide and a digit thick; the lowest is at a distance of one foot from the
middle one, and the middle one a distance of two feet from the upper one.
Under them are eighteen iron bars fixed by iron rivets; these bars are of
the same width and thickness as the bands, and they are of such a length, that
curving, they reach from the lower band to the upper, that is two feet and
three palms long, while the dome is only one foot and three palms high. All
the bars and bands of the dome have iron plates fastened on the underside
with iron wire. In addition, the dome has four apertures; the rear one,
which is situated opposite the channel through which the litharge flows out,
is two feet wide at the bottom; toward the top, since it slopes gently, it is
narrower, being a foot, three palms, and a digit wide; there is no bar at
this place, for the aperture extends from the upper band to the middle one,
but not to the lower one. The second aperture is situated above the
ARECTANGULAR STONES. BSOLE−STONE. CAIR−HOLES. DINTERNAL WALLS.
EDOME. FCRUCIBLE. GBANDS. HBARS. IAPERTURES IN THE DOME.
KLID OF THE DOME. LRINGS. MPIPES. NVALVES. OCHAINS.
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channel, is two and a half feet wide at the bottom, and two feet and a palm
at the top; and there is likewise no bar at this point; indeed, not only does
the bar not extend to the lower band, but the lower band itself does not
extend over this part, in order that the master can draw the litharge out
of the crucible. There are besides, in the wall which protects the principal
wall against the heat, near where the nozzles of the bellows are situated,
two apertures, three palms wide and about a foot high, in the middle
of which two rods descend, fastened on the inside with plates.
Near these apertures are placed the nozzles of the bellows, and through
the apertures extend the pipes in which the nozzles of the bellows are
set. These pipes are made of iron plates rolled up; they are two
palms three digits long, and their inside diameter is three and a half
digits; into these two pipes the nozzles of the bellows penetrate a distance of
three digits from their valves. The lid of the dome consists of an iron band
at the bottom, two digits wide, and of three curved iron bars, which extend
from one point on the band to the point opposite; they cross each other at
the top, where they are fixed by means of iron rivets. On the under side of
the bars there are likewise plates fastened by rivets; each of the plates has
small holes the size of a finger, so that the lute will adhere when the interior
is lined. The dome has three iron rings engaged in wide holes in the heads of
iron claves, which fasten the bars to the middle band at these points. Into
these rings are fastened the hooks of the chains with which the dome is
raised, when the master is preparing the crucible.
On the sole and the copper plates and the rock of the furnace, lute mixed
with straw is placed to a depth of three digits, and it is pounded with a wooden
rammer until it is compressed to a depth of one digit only. The rammer−head
is round and three palms high, two palms wide at the bottom, and tapering
upward; its handle is three feet long, and where it is set into the rammer−
head it is bound around with an iron band. The top of the stonework in
which the dome rests is also covered with lute, likewise mixed with straw,
to the thickness of a palm. All this, as soon as it becomes loosened, must
be repaired.
The artificer who undertakes the work of parting the metals, distributes
the operation into two shifts of two days. On the one morning he sprinkles
a little ash into the lute, and when he has poured some water over it he brushes
it over with a broom. Then he throws in sifted ashes and dampens them
with water, so that they could be moulded into balls like snow. The ashes
are those from which lye has been made by letting water percolate
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through them, for other ashes which are fatty would have to be burnt
again in order to make them less fat. When he has made the ashes
smooth by pressing them with his hands, he makes the crucible slope down
toward the middle; then he tamps it, as I have described, with a rammer.
He afterward, with two small wooden rammers, one held in each hand,
forms the channel through which the litharge flows out. The heads of these
small rammers are each a palm wide, two digits thick, and one foot high;
the handle of each is somewhat rounded, is a digit and a half less in
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AAN ARTIFICER TAMPING THE CRUCIBLE WITH A RAMMER. BLARGE RAMMER.
CBROOM. DTWO SMALLER RAMMERS. ECURVED IRON PLATES. FPART OF
A WOODEN STRIP. GSIEVE. HASHES. IIRON SHOVEL. KIRON PLATE.
LBLOCK OF WOOD. MROCK. NBASKET MADE OF WOVEN TWIGS. OHOOKED
BAR. PSECOND HOOKED BAR. QOLD LINEN RAG. RBUCKET. SDOESKIN.
TBUNDLES OF STRAW. VWOOD. XCAKES OF LEAD ALLOY. YFORK.
ZANOTHER WORKMAN COVERS THE OUTSIDE OF THE FURNACE WITH LUTE WHERE THE
DOME FITS ON IT. AABASKET FULL OF ASHES. BBLID OF THE DOME. CCTHE
ASSISTANT STANDING ON THE STEPS POURS CHARCOAL INTO THE CRUCIBLE THROUGH
THE
HO AT THE TOP OF THE DOME. DDIRON IMPLEMENT WITH WHICH THE LUTE IS
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diameter than the rammer−head, and is three feet in length; the rammer−
head as well as the handle is made of one piece of wood. Then with shoes on,
he descends into the crucible and stamps it in every direction with his feet,
in which manner it is packed and made sloping. Then he again tamps it
with a large rammer, and removing his shoe from his right foot he draws a circle
around the crucible with it, and cuts out the circle thus drawn with an iron
plate. This plate is curved at both ends, is three palms long, as many digits
wide, and has wooden handles a palm and two digits long, and two digits
thick; the iron plate is curved back at the top and ends, which penetrate
into handles. There are some who use in the place of the plate a strip of
wood, like the rim of a sieve; this is three digits wide, and is cut out at both
ends that it may be held in the hands. Afterward he tamps the channel
through which the litharge discharges. Lest the ashes should fall out, he
blocks up the aperture with a stone shaped to fit it, against which he places
a board, and lest this fall, he props it with a stick. Then he pours in
a basketful of ashes and tamps them with the large rammer; then again and
again he pours in ashes and tamps them with the rammer. When the
channel has been made, he throws dry ashes all over the crucible with a sieve,
and smooths and rubs it with his hands. Then he throws three basketsful
of damp ashes on the margin all round the edge of the crucible, and lets down
the dome. Soon after, climbing upon the crucible, he builds up ashes all
around it, lest the molten alloy should flow out. Then, having raised the lid of
the dome, he throws a basketful of charcoal into the crucible, together with
an iron shovelful of glowing coals, and he also throws some of the latter
through the apertures in the sides of the dome, and he spreads them with the
same shovel. This work and labour is finished in the space of two hours.
An iron plate is set in the ground under the channel, and upon this is
placed a wooden block, three feet and a palm long, a foot and two palms and
as many digits wide at the back, and two palms and as many digits wide in
front; on the block of wood is placed a stone, and over it an iron plate similar
to the bottom one, and upon this he puts a basketful of charcoal, and also
an iron shovelful of burning charcoals. The crucible is heated in an
hour, and then, with the hooked bar with which the litharge is drawn off, he
stirs the remainder of the charcoal about. This hook is a palm long and three
digits wide, has the form of a double triangle, and has an iron handle four
feet long, into which is set a wooden one six feet long. There are some who
use instead a simple hooked bar. After about an hour' s time, he stirs the
charcoal again with the bar, and with the shovel throws into the crucible
the burning charcoals lying in the channel; then again, after the space of an
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hour, he stirs the burning charcoals with the same bar. If he did not thus
stir them about, some blackness would remain in the crucible and that part
would be damaged, because it would not be sufficiently dried. Therefore
the assistant stirs and turns the burning charcoal that it may be entirely
burnt up, and so that the crucible may be well heated, which takes three
hours; then the crucible is left quiet for the remaining two hours.
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When the hour of eleven has struck, he sweeps up the charcoal ashes with
a broom and throws them out of the crucible. Then he climbs on to the
dome, and passing his hand in through its opening, and dipping an old linen
rag in a bucket of water mixed with ashes, he moistens the whole of the
crucible and sweeps it. In this way he uses two bucketsful of the mixture,
each holding five Roman sextaríi, 28 and he does this lest the crucible,
when the metals are being parted, should break open; after this he rubs the
crucible with a doe skin, and fills in the cracks. Then he places at the left side
of the channel, two fragments of hearth−lead, laid one on the top of the other,
so that when partly melted they remain fixed and form an obstacle, that the
litharge will not be blown about by the wind from the bellows, but remain in
its place. It is expedient, however, to use a brick in the place of the hearth−
lead, for as this gets much hotter, therefore it causes the litharge to form
more rapidly. The crucible in its middle part is made two palms and as
many digits deeper. 29
There are some who having thus prepared the crucible, smear it over
with incense 30 , ground to powder and dissolved in white of egg, soaking
it up in a sponge and then squeezing it out again; there are others who
smear over it a liquid consisting of white of egg and double the amount of
bullock' s blood or marrow. Some throw lime into the crucible through a
sieve.
Afterward the master of the works weighs the lead with which the gold
or silver or both are mixed, and he sometimes puts a hundred centumpondía 31
into the crucible, but frequently only sixty, or fifty, or much less. After it
has been weighed, he strews about in the crucible three small bundles of
straw, lest the lead by its weight should break the surface. Then he places
in the channel several cakes of lead alloy, and through the aperture at the rear
of the dome he places some along the sides; then, ascending to the opening at
the top of the dome, he arranges in the crucible round about the dome the
cakes which his assistant hands to him, and after ascending again and passing
his hands through the same aperture, he likewise places other cakes inside the
crucible. On the second day those which remain he, with an iron fork,
places on the wood through the rear aperture of the dome.
When the cakes have been thus arranged through the hole at the top of
the dome, he throws in charcoal with a basket woven of wooden twigs. Then
he places the lid over the dome, and the assistant covers over the joints with
lute. The master himself throws half a basketful of charcoal into the crucible
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through the aperture next to the nozzle pipe, and prepares the bellows, in
order to be able to begin the second operation on the morning of the following
day. It takes the space of one hour to carry out such a piece of work, and
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at twelve all is prepared. These hours all reckoned up make a sum of eight
hours.
Now it is time that we should come to the second operation. In the
morning the workman takes up two shovelsful of live charcoals and throws
them into the crucible through the aperture next to the pipes of the nozzles;
then through the same hole he lays upon them small pieces of fir−wood or of
pitch pine, such as are generally used to cook fish. After this the water−gates
are opened, in order that the machine may be turned which depresses the levers
of the bellows. In the space of one hour the lead alloy is melted; and when this
has been done, he places four sticks of wood, twelve feet long, through the
hole in the back of the dome, and as many through the channel; these
sticks, lest they should damage the crucible, are both weighted on the ends
and supported by trestles; these trestles are made of a beam, three feet
long, two palms and as many digits wide, two palms thick, and have two
spreading legs at each end. Against the trestle, in front of the channel, there
is placed an iron plate, lest the litharge, when it is extracted from the furnace,
should splash the smelter' s shoes and injure his feet and legs. With an iron
shovel or a fork he places the remainder of the cakes through the aperture at
the back of the dome on to the sticks of wood already mentioned.
The native silver, or silver glance, or grey silver, or ruby silver, or any
other sort, when it has been flattened out 32 , and cut up, and heated in an
iron crucible, is poured into the molten lead mixed with silver, in order that
impurities may be separated. As I have often said, this molten lead mixed
with silver is called stannum 33 .
When the long sticks of wood are burned up at the fore end, the
master, with a hammer, drives into them pointed iron bars, four feet long and
two digits wide at the front end, and beyond that one and a half digits wide
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and thick with these he pushes the sticks of wood forward and the bars
then rest on the trestles. There are others who, when they separate metals,
put two such sticks of wood into the crucible through the aperture which is
between the bellows, as many through the holes at the back, and one through
the channel; but in this case a larger number of long sticks of wood is
necessary, that is, sixty; in the former case, forty long sticks of wood suffice
to carry out the operation. When the lead has been heated for two hours,
it is stirred with a hooked bar, that the heat may be increased.
If it be difficult to separate the lead from the silver, he throws copper
and charcoal dust into the molten silver−lead alloy. If the alloy of argen−
tiferous gold and lead, or the silver−lead alloy, contains impurities from the
ore, then he throws in either equal portions of argol and Venetian glass or of
sal−ammoniac, or of Venetian glass and of Venetian soap; or else unequal
portions, that is, two of argol and one of iron rust; there are some who
mix a little saltpetre with each compound. To one centumpondium of the
alloy is added a bes or a líbra and a third of the powder, according
to whether it is more or less impure. The powder certainly separates the
impurities from the alloy. Then, with a kind of rabble he draws out through
AFURNACE. BSTICKS OF WOOD. CLITHARGE. DPLATE. ETHE FOREMAN
WHEN HUNGRY EATS BUTTER, THAT THE POISON WHICH THE CRUCIBLE EXHALES MAY
NOT
HARM HIM, FOR THIS IS A SPECIAL REMEDY AGAINST THAT POISON.
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the channel, mixed with charcoal, the scum, as one might say, of the lead;
the lead makes this scum when it becomes hot, but that less of it may be
made it must be stirred frequently with the bar.
Within the space of a quarter of an hour the crucible absorbs the lead;
at the time when it penetrates into the crucible it leaps and bubbles. Then
the master takes out a little lead with an iron ladle, which he assays, in order
to find what proportion of silver there is in the whole of the alloy; the
ladle is five digits wide, the iron part of its handle is three feet long and the
wooden part the same. Afterward, when they are heated, he extracts with
a bar the litharge which comes from the lead and the copper, if there be any
of it in the alloy. Wherefore, it might more rightly be called spuma of lead
than of silver 34 . There is no injury to the silver, when the lead and copper
are separated from it. In truth the lead becomes much purer in the crucible
of the other furnace, in which silver is refined. In ancient times, as the
author Pliny 35 relates, there was under the channel of the crucible another
crucible, and the litharge flowed down from the upper one into the lower
one, out of which it was lifted up and rolled round with a stick in order that
it might be of moderate weight. For which reason, they formerly made it
into small tubes or pipes, but now, since it is not rolled round a stick, they
make it into bars.
If there be any danger that the alloy might flow out with the litharge, the
foreman keeps on hand a piece of lute, shaped like a cylinder and pointed at
both ends; fastening this to a hooked bar he opposes it to the alloy so that
it will not flow out.
Now when the colour begins to show in the silver, bright spots appear,
some of them being almost white, and a moment afterward it becomes
absolutely white. Then the assistant lets down the water−gates, so that, the
race being closed, the water−wheel ceases to turn and the bellows are still.
Then the master pours several buckets of water on to the silver to cool it;
others pour beer over it to make it whiter, but this is of no importance since
the silver has yet to be refined. Afterward, the cake of silver is raised with
the pointed iron bar, which is three feet long and two digits wide, and has a
wooden handle four feet long fixed in its socket. When the cake of silver has
been taken from the crucible, it is laid upon a stone, and from part of it the
hearth−lead, and from the other part the litharge, is chipped away with a
hammer; then it is cleansed with a bundle of brass wire dipped in water.
When the lead is separated from the silver, more silver is frequently found
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than when it was assayed; for instance, if before there were three uncíae and
as many drachmae in a centumpondíum, they now sometimes find three uncíae
and a half 36 . Often the hearth−lead remaining in the crucible is a palm
deep; it is taken out with the rest of the ashes and is sifted, and that which
remains in the sieve, since it is hearth−lead, is added to the hearth−lead 37 .
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ACAKE. BSTONE. CHAMMER. DBRASS WIRE. EBUCKET CONTAINING WATER.
FFURNACE FROM WHICH THE CAKE HAS BEEN TAKEN, WHICH IS STILL SMOKING.
GLABOURER CARRYING A CAKE OUT OF THE WORKS.
The ashes which pass through the sieve are of the same use as they were
at first, for, indeed, from these and pulverised bones they make the cupels.
Finally, when much of it has accumulated, the yellow pompholyx adhering to
the walls of the furnace, and likewise to those rings of the dome near the
apertures, is cleared away.
I must also describe the crane with which the dome is raised. When
it is made, there is first set up a rectangular upright post twelve feet
long, each side of which measures a foot in width. Its lower pinion turns
in a bronze socket set in an oak sill; there are two sills placed crosswise so
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that the one fits in a mortise in the middle of the other, and the other likewise
fits in the mortise of the first, thus making a kind of a cross; these sills are
three feet long and one foot wide and thick. The crane−post is round at its
upper end and is cut down to a depth of three palms, and turns in a band
fastened at each end to a roof−beam, from which springs the inclined chimney
wall. To the crane−post is affixed a frame, which is made in this way: first, at a
height of a cubit from the bottom, is mortised into the crane−post a small
cross−beam, a cubit and three digits long, except its tenons, and two palms in
width and thickness. Then again, at a height of five feet above it, is another
small cross−beam of equal length, width, and thickness, mortised into the
crane−post. The other ends of these two small cross−beams are mortised
into an upright timber, six feet three palms long, and three−quarters wide
and thick; the mortise is transfixed by wooden pegs. Above, at a height of
three palms from the lower small cross−beam, are two bars, one foot one palm
long, not including the tenons, a palm three digits wide, and a palm thick,
which are mortised in the other sides of the crane−post. In the same manner,
under the upper small cross−beam are two bars of the same size. Also in the
upright timber there are mortised the same number of bars, of the same length
as the preceding, but three digits thick, a palm two digits wide, the two
lower ones being above the lower small cross−beam. From the upright
timber near the upper small cross−beam, which at its other end is mortised
into the crane−post, are two mortised bars. On the outside of this frame,
boards are fixed to the small cross−beams, but the front and back parts of the
frame have doors, whose hinges are fastened to the boards which are fixed
to the bars that are mortised to the sides of the crane−post.
Then boards are laid upon the lower small cross−beam, and at a height
of two palms above these there is a small square iron axle, the sides of which
are two digits wide; both ends of it are round and turn in bronze or iron
bearings, one of these bearings being fastened in the crane−post, the other in
the upright timber. About each end of the small axle is a wooden disc, of three
palms and a digit radius and one palm thick, covered on the rim with an iron
band; these two discs are distant two palms and as many digits from each
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other, and are joined with five rundles; these rundles are two and a half
digits thick and are placed three digits apart. Thus a drum is made, which
is a palm and a digit distant from the upright timber, but further from the
crane−post, namely, a palm and three digits. At a height of a foot and a
palm above this little axle is a second small square iron axle, the thickness of
which is three digits; this one, like the first one, turns in bronze or iron
bearings. Around it is a toothed wheel, composed of two discs a foot three
palms in diameter, a palm and two digits thick: on the rim of this there
are twenty−three teeth, a palm wide and two digits thick; they protrude
a palm from the wheel and are three digits apart. And around this same
axle, at a distance of two palms and as many digits toward the upright
timber, is another disc of the same diameter as the wheel and a palm thick;
this turns in a hollowed−out place in the upright timber. Between this disc
and the disc of the toothed wheel another drum is made, having likewise five
rundles. There is, in addition to this second axle, at a height of a cubit
above it, a small wooden axle, the journals of which are of iron; the ends
are bound round with iron rings so that the journals may remain firmly fixed,
and the journals, like the little iron axles, turn in bronze or iron bearings.
This third axle is at a distance of about a cubit from the upper small cross−
beam; it has, near the upright timber, a toothed wheel two and a half feet
in diameter, on the rim of which are twenty−seven teeth; the other part of
this axle, near the crane−post, is covered with iron plates, lest it should be worn
away by the chain which winds around it. The end link of the chain is fixed
in an iron pin driven into the little axle; this chain passes out of the frame
and turns over a little pulley set between the beams of the crane−arm.
Above the frame, at a height of a foot and a palm, is the crane−arm. This
consists of two beams fifteen feet long, three palms wide, and two thick,
mortised into the crane−post, and they protrude a cubit from the back of the
crane−post and are fastened together. Moreover, they are fastened by means
of a wooden pin which penetrates through them and the crane−post; this
pin has at the one end a broad head, and at the other a hole, through which
is driven an iron bolt, so that the beams may be tightly bound into the crane−
post. The beams of the crane−arm are supported and stayed by means of
two oblique beams, six feet and two palms long, and likewise two palms wide
and thick; these are mortised into the crane−post at their lower ends, and
their upper ends are mortised into the beams of the crane−arm at a point
about four feet from the crane−post, and they are fastened with iron nails.
At the back of the upper end of these oblique beams, toward the crane−post,
is an iron staple, fastened into the lower sides of the beams of the crane−arm, in
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order that it may hold them fast and bind them. The outer end of each
beam of the crane−arm is set in a rectangular iron plate, and between these
are three rectangular iron plates, fixed in such a manner that the beams of the
crane−arm can neither move away from, nor toward, each other. The upper
sides of these crane−arm beams are covered with iron plates for a length of
six feet, so that a trolley can move on it.
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ACRANE−POST. BSOCKET. COAK CROSS−SILLS. DBAND. EROOF−BEAM.
FFRAME. GLOWER SMALL CROSS−BEAM. HUPRIGHT TIMBER. IBARS WHICH
COME FROM THE SIDES OF THE CRANE−POST. KBARS WHICH COME FROM THE SIDES OF
THE UPRIGHT TIMBER. LRUNDLE DRUMS. MTOOTHED WHEELS. NCHAIN.
OPULLEY. PBEAMS OF THE CRANE−ARM. QOBLIQUE BEAMS SUPPORTING THE BEAMS
OF THE CRANE−ARM. RRECTANGULAR IRON PLATES. STROLLEY. TDOME OF THE
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The body of the trolley is made of wood from the Ostrya or any other
hard tree, and is a cubit long, a foot wide, and three palms thick; on both
edges of it the lower side is cut out to a height and width of a palm, so that
the remainder may move backward and forward between the two beams of
the crane−arm; at the front, in the middle part, it is cut out to a width of
two palms and as many digits, that a bronze pulley, around a small iron
axle, may turn in it. Near the corners of the trolley are four holes, in which
as many small wheels travel on the beams of the crane−arm. Since this
trolley, when it travels backward and forward, gives out a sound somewhat
similar to the barking of a dog, we have given it this name 38 . It is propelled
forward by means of a crank, and is drawn back by means of a chain. There
is an iron hook whose ring turns round an iron pin fastened to the right side
of the trolley, which hook is held by a sort of clavis, which is fixed in the
right beam of the crane−arm.
At the end of the crane−post is a bronze pulley, the iron axle of which is
fastened in the beams of the crane−arm, and over which the chain passes
as it comes from the frame, and then, penetrating through the hollow in the
top of the trolley, it reaches to the little bronze pulley of the trolley, and passing
over this it hangs down. A hook on its end engages a ring, in which are
fixed the top links of three chains, each six feet long, which pass through
the three iron rings fastened in the holes of the claves which are fixed into
the middle iron band of the dome, of which I have spoken.
Therefore when the master wishes to lift the dome by means of the
crane, the assistant fits over the lower small iron axle an iron crank, which
projects from the upright beam a palm and two digits; the end of the little
axle is rectangular, and one and a half digits wide and one digit thick; it is
set into a similar rectangular hole in the crank, which is two digits long and a
little more than a digit wide. The crank is semi−circular, and one foot three
palms and two digits long, as many digits wide, and one digit thick. Its
handle is straight and round, and three palms long, and one and a half digits
thick. There is a hole in the end of the little axle, through which an iron
pin is driven so that the crank may not come off. The crane having four
drums, two of which are rundle−drums and two toothed−wheels, is more easily
moved than another having two drums, one of which has rundles and the
other teeth.
Many, however, use only a simple contrivance, the pivots of whose
crane−post turn in the same manner, the one in an iron socket, the other in a
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ring. There is a crane−arm on the crane−post, which is supported by an
oblique beam; to the head of the crane−arm a strong iron ring is fixed,
which engages a second iron ring. In this iron ring a strong wooden lever−bar
is fastened firmly, the head of which is bound by a third iron ring, from which
hangs an iron hook, which engages the rings at the ends of the chains from
the dome. At the other end of the lever−bar is another chain, which, when
it is pulled down, raises the opposite end of the bar and thus the dome; and
when it is relaxed the dome is lowered.
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ACHAMBER OF THE FURNACE. BITS BED. CPASSAGES. DRAMMER.
EMALLET. FARTIFICER MAKING TUBES FROM LITHARGE ACCORDING TO THE ROMAN
METHOD. GCHANNEL. HLITHARGE. ILOWER CRUCIBLE OR HEARTH. KSTICK.
LTUBES.
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In certain places, as at Freiberg in Meissen, the upper part of the
cupellation furnace is vaulted almost like an oven. This chamber is four
feet high and has either two or three apertures, of which the first, in
front, is one and a half feet high and a foot wide, and out of this flows
the litharge; the second aperture and likewise the third, if there be three,
are at the sides, and are a foot and a half high and two and a half feet wide,
in order that he who prepares the crucible may be able to creep into the
furnace. Its circular bed is made of cement, it has two passages two feet high
and one foot wide, for letting out the vapour, and these lead directly through
from one side to the other, so that the one passage crosses the other at right
angles, and thus four openings are to be seen; these are covered at the top
by rocks, wide, but only a palm thick. On these and on the other parts
of the interior of the bed made of cement, is placed lute mixed with straw,
to a depth of three digits, as it was placed over the sole and the plates of
copper and the rocks of that other furnace. This, together with the ashes which
are thrown in, the master or the assistant, who, upon his knees, prepares
the crucible, tamps down with short wooden rammers and with mallets
likewise made of wood.
AFURNACE SIMILAR TO AN OVEN. BPASSAGE CIRON BARS. DHOLE THROUGH
WHICH THE LITHARGE IS DRAWN OUT. ECRUCIBLE WHICH LACKS A DOME. FTHICK
STICKS. GBELLOWS
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The cupellation furnace in Poland and Hungary is likewise vaulted at the
top, and is almost similar to an oven, but in the lower part the bed is solid,
and there is no opening for the vapours, while on one side of the crucible is a
wall, between which and the bed of the crucible is a passage in place of the
opening for vapours; this passage is covered by iron bars or rods extending
from the wall to the crucible, and placed a distance of two digits from each
other. In the crucible, when it is prepared, they first scatter straw, and then
they lay in it cakes of silver−lead alloy, and on the iron bars they lay wood,
which when kindled heats the crucible. They melt cakes to the weight of some−
times eighty centumpondia and sometimes a hundred centumpondia 39 . They
stimulate a mild fire by means of a blast from the bellows, and throw on to the
bars as much wood as is required to make a flame which will reach into the
crucible, and separate the lead from the silver. The litharge is drawn out
on the other side through an aperture that is just wide enough for the master
to creep through into the crucible. The Moravians and Carni, who very
rarely make more than a bes or five−sixths of a libra of silver, separate
the lead from it, neither in a furnace resembling an oven, nor in the crucible
covered by a dome, but on a crucible which is without a cover and exposed to
the wind; on this crucible they lay cakes of silver−lead alloy, and over them
they place dry wood, and over these again thick green wood. The wood
having been kindled, they stimulate the fire by means of a bellows.
I have explained the method of separating lead from gold or silver. Now
I will speak of the method of refining silver, for I have already explained
the process for refining gold. Silver is refined in a refining furnace,
over whose hearth is an arched chamber built of bricks; this chamber
in the front part is three feet high. The hearth itself is five feet long
an four wide. The walls are unbroken along the sides and back, but
in front one chamber is placed over the other, and above these and the
wall is the upright chimney. The hearth has a round pit, a cubit wide and two
palms deep, into which are thrown sifted ashes, and in this is placed a prepared
earthenware "test," in such a manner that it is surrounded on all sides
by ashes to a height equal to its own. The earthenware test is filled
with a powder consisting of equal portions of bones ground to powder, and of
ashes taken from the crucible in which lead is separated from gold or silver;
others mix crushed brick with the ashes, for by this method the powder
attracts no silver to itself. When the powder has been made up and
moistened with water, a little is thrown into the earthenware test and tamped
with a wooden pestle. This pestle is round, a foot long, and a palm and a
digit wide, out of which extend six teeth, each a digit thick, and a digit and a
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third long and wide, and almost a digit apart; these six teeth form a circle,
and in the centre of them is the seventh tooth, which is round and of the
same length as the others, but a digit and a half thick; this pestle tapers a
little from the bottom up, that the upper part of the handle may be round
and three digits thick. Some use a round pestle without teeth. Then a
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APESTLE WITH TEETH. BPESTLE WITHOUT TEETH. CDISH OR TRAY FULL OF ASHES.
DPREPARED TESTS PLACED ON BOARDS OR SHELVES. EEMPTY TESTS. FWOOD.
GSAW.
little powder is again moistened, and thrown into the test, and tamped; this
work is repeated until the test is entirely full of the powder, which the
master then cuts out with a knife, sharp on both sides, and turned upward at
both ends so that the central part is a palm and a digit long; therefore it is
partly straight and partly curved. The blade is one and a half digits wide,
and at each end it turns upward two palms, which ends to the depth of a
palm are either not sharpened or they are enclosed in wooden handles. The
master holds the knife with one hand and cuts out the powder from the test,
so that it is left three digits thick all round; then he sifts the powder of dried
bones over it through a sieve, the bottom of which is made of closely−woven
bristles. Afterward a ball made of very hard wood, six digits in diameter,
is placed in the test and rolled about with both hands, in order to make the
inside even and smooth; for that matter he may move the ball about with only
one hand. The tests 40 are of various capacities, for some of them when prepared
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ASTRAIGHT KNIFE HAVING WOODEN HANDLES. BCURVED KNIFE LIKEWISE HAVING
WOODEN HANDLES. CCURVED KNIFE WITHOUT WOODEN HANDLES. DSIEVE.
EBALLS. FIRON DOOR WHICH THE MASTER LETS DOWN WHEN HE REFINES SILVER, LEST
THE HEAT OF THE FIRE SHOULD INJURE HIS EYES. GIRON IMPLEMENT ON WHICH THE
WOOD IS PLACED WHEN THE LIQUID SILVER IS TO BE REFINED. HITS OTHER PART
PASSING THROUGH THE RING OF ANOTHER IRON IMPLEMENT ENCLOSED IN THE WALL OF
THE
FURNACE. ITESTS IN WHICH BURNING CHARCOAL HAS BEEN THROWN.
hold much less than fifteen librae of silver, others twenty, some thirty, others
forty, and others fifty. All these tests thus prepared are dried in the sun, or
set in a warm and covered place; the more dry and old they are the better.
All of them, when used for refining silver, are heated by means of burning
charcoal placed in them. Others use instead of these tests an iron ring; but
the test is more useful, for if the powder deteriorates the silver remains in
it, while there being no bottom to the ring, it falls out; besides, it is easier to
place in the hearth the test than the iron ring, and furthermore it requires
much less powder. In order that the test should not break and damage the
silver, some bind it round with an iron band.
In order that they may be more easily broken, the silver cakes are placed
upon an iron grate by the refiner, and are heated by burning charcoal
placed under them. He has a brass block two palms and two digits long and
wide, with a channel in the middle, which he places upon a block of hard
wood. Then with a double−headed hammer, he beats the hot cakes of silver
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placed on the brass block, and breaks them in pieces. The head of this
hammer is a foot and two digits long, and a palm wide. Others use for this
purpose merely a block of wood channelled in the top. While the fragments
of the cake are still hot, he seizes them with the tongs and throws them into
a bowl with holes in the bottom, and pours water over them. When the
fragments are cooled, he puts them nicely into the test by placing them so
that they stand upright and project from the test to a height of two palms, and
lest one should fall against the other, he places little pieces of charcoal between
them; then he places live charcoal in the test, and soon two twig basketsful
of charcoal. Then he blows in air with the bellows. This bellows is double,
and four feet two palms long, and two feet and as many palms wide at the
back; the other parts are similar to those described in Book VII. The
nozzle of the bellows is placed in a bronze pipe a foot long, the aperture in
this pipe being a digit in diameter in front and quite round, and at the back
two palms wide. The master, because he needs for the operation of refining
AGRATE. BBRASS BLOCK. CBLOCK OF WOOD. DCAKES OF SILVER. EHAMMER.
FBLOCK OF WOOD CHANNELLED IN THE MIDDLE. GBOWL FULL OF HOLES.
HBLOCK OF WOOD FASTENED TO AN IRON IMPLEMENT. IFIR−WOOD. KIRON BAR.
LIMPLEMENT WITH A HOLLOW END. THE IMPLEMENT WHICH HAS A CIRCULAR END IS
SHOWN IN THE NEXT PICTURE. MIMPLEMENT, THE EXTREMITY OF WHICH IS BENT
UPWARDS. NIMPLEMENT IN THE SHAPE OF TONGS.
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silver a fierce fire, and requires on that account a vigorous blast, places the
bellows very much inclined, in order that, when the silver has melted, it
may blow into the centre of the test. When the silver bubbles, he presses the
nozzle down by means of a small block of wood moistened with water and
fastened to an iron rod, the outer end of which bends upward. The silver
melts when it has been heated in the test for about an hour; when it is
melted, he removes the live coals from the test and places over it two billets
of fir−wood, a foot and three palms long, a palm two digits wide, one palm
thick at the upper part, and three digits at the lower. He joins them
together at the lower edges, and into the billets he again throws the coals,
for a fierce fire is always necessary in refining silver. It is refined in two or
three hours, according to whether it was pure or impure, and if it is impure it
is made purer by dropping granulated copper or lead into the test at the
same time. In order that the refiner may sustain the great heat from the fire
while the silver is being refined, he lets down an iron door, which is three feet
long and a foot and three palms high; this door is held on both ends in iron
plates, and when the operation is concluded, he raises it again with an iron
shovel, so that its edge holds against the iron hook in the arch, and thus the
door is held open. When the silver is nearly refined, which may be judged
by the space of time, he dips into it an iron bar, three and a half feet
long and a digit thick, having a round steel point. The small drops of silver
that adhere to the bar he places on the brass block and flattens with
a hammer, and from their colour he decides whether the silver is sufficiently
refined or not. If it is thoroughly purified it is very white, and in a bes there
is only a drachma of impurities. Some ladle up the silver with a hollow iron
implement. Of each bes of silver one sicilicus is consumed, or occasionally
when very impure, three drachmae or half an uncia 41 .
The refiner governs the fire and stirs the molten silver with an iron
implement, nine feet long, a digit thick, and at the end first curved toward
the right, then curved back in order to form a circle, the interior of which is a
palm in diameter; others use an iron implement, the end of which is bent
directly upward. Another iron implement has the shape of tongs, with
which, by compressing it with his hands, he seizes the coals and puts them on
or takes them off; this is two feet long, one and a half digits wide, and the
third of a digit thick.
When the silver is seen to be thoroughly refined, the artificer removes
the coals from the test with a shovel. Soon afterward he draws water in
a copper ladle, which has a wooden handle four feet long; it has a small
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hole at a point half−way between the middle of the bowl and the edge, through
which a hemp seed just passes. He fills this ladle three times with water,
and three times it all flows out through the hole on to the silver, and slowly
quenches it; if he suddenly poured much water on it, it would burst asunder
and injure those standing near. The artificer has a pointed iron bar, three
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AIMPLEMENT WITH A RING. BLADLE. CITS HOLE. DPOINTED BAR. EFORKS.
FCAKE OF SILVER LAID UPON THE IMPLEMENT SHAPED LIKE TONGS. GTUB OF WATER.
HBLOCK OF WOOD, WITH A CAKE LAID UPON IT. IHAMMER. KSILVER AGAIN
PLACED UPON THE IMPLEMENT RESEMBLING TONGS. LANOTHER TUB FULL OF WATER.
MBRASS WIRES. NTRIPOD. OANOTHER BLOCK. PCHISEL. QCRUCIBLE OF
THE FURNACE. RTEST STILL SMOKING.
feet long, which has a wooden handle as many feet long, and he puts the end of
this bar into the test in order to stir it. He also stirs it with a hooked iron
bar, of which the hook is two digits wide and a palm deep, and the iron part
of its handle is three feet long and the wooden part the same. Then he
removes the test from the hearth with a shovel or a fork, and turns it over,
and by this means the silver falls to the ground in the shape of half a sphere;
then lifting the cake with a shovel he throws it into a tub of water, where
it gives out a great sound. Or else, having lifted the cake of silver with a
fork, he lays it upon the iron implement similar to tongs, which are placed
across a tub full of water; afterward, when cooled, he takes it from the
tub again and lays it on the block made of hard wood and beats it with a
hammer, in order to break off any of the powder from the test which
adheres to it. The cake is then placed on the implement similar to
tongs, laid over the tub full of water, and cleaned with a bundle of brass wire
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dipped into the water; this operation of beating and cleansing is repeated
until it is all clean. Afterward he places it on an iron grate or tripod; the
tripod is a palm and two digits high, one and a half digits wide, and its span
is two palms wide; then he puts burning charcoal under the tripod or grate,
in order again to dry the silver that was moistened by the water. Finally,
the Royal Inspector 42 in the employment of the King or Prince, or the owner,
lays the silver on a block of wood, and with an engraver' s chisel he cuts out two
AMUFFLE. BITS LITTLE WINDOWS. CITS LITTLE BRIDGE. DBRICKS. EIRON
DOOR. FITS LITTLE WINDOW. GBELLOWS. HHAMMER−CHISEL. IIRON RING
WHICH SOME USE INSTEAD OF THE TEST. KPESTLE WITH WHICH THE ASHES PLACED IN
THE RING ARE POUNDED.
small pieces, one from the under and the other from the upper side. These
are tested by fire, in order to ascertain whether the silver is thoroughly refined
or not, and at what price it should be sold to the merchants. Finally he
impresses upon it the seal of the King or the Prince or the owner, and, near
the same, the amount of the weight.
There are some who refine silver in tests placed under iron or earthen−
ware muffles. They use a furnace, on the hearth of which they place the test
containing the fragments of silver, and they place the muffle over it; the
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muffle has small windows at the sides, and in front a little bridge. In order
to melt the silver, at the sides of the muffle are laid bricks, upon which the
charcoal is placed, and burning firebrands are put on the bridge. The
furnace has an iron door, which is covered on the side next to the fire with lute
in order that it may not be injured. When the door is closed it retains the
heat of the fire, but it has a small window, so that the artificers may look
into the test and may at times stimulate the fire with the bellows. Although
by this method silver is refined more slowly than by the other, nevertheless it is
more useful, because less loss is caused, for a gentle fire consumes fewer particles
than a fierce fire continually excited by the blast of the bellows. If, on
account of its great size, the cake of silver can be carried only with difficulty
when it is taken out of the muffle, they cut it up into two or three
pieces while it is still hot, with a wedge or a hammer−chisel; for if they cut
it up after it has cooled, little pieces of it frequently fly off and are lost.
END OF BOOK X.