Book XII

BOOK XII.
Previously I have dealt with the methods of
separating silver from copper. There now remains
the portion which treats of solidified juices; and
whereas they might be considered as alien to things
metallic, nevertheless, the reasons why they should
not be separated from it I have explained in the
second book.
Solidified juices are either prepared from waters
in which nature or art has infused them, or they are
produced from the liquid juices themselves, or from stony minerals. Sagacious
people, at first observing the waters of some lakes to be naturally full of juices
which thickened on being dried up by the heat of the sun and thus became
solidified juices, drew such waters into other places, or diverted them
into low−lying places adjoining hills, so that the heat of the sun should
likewise cause them to condense. Subsequently, because they observed that
in this wise the solidified juices could be made only in summer, and then
not in all countries, but only in hot and temperate regions in which it seldom
rains in summer, they boiled them in vessels over a fire until they began to
thicken. In this manner, at all times of the year, in all regions, even the
coldest, solidified juices could be obtained from solutions of such juices,
whether made by nature or by art. Afterward, when they saw juices
drip from some roasted stones, they cooked these in pots in order to obtain
solidified juices in this wise also. It is worth the trouble to learn the pro−
portions and the methods by which these are made.
I will therefore begin with salt, which is made from water either salty
by nature, or by the labour of man, or else from a solution of salt, or
from lye, likewise salty. Water which is salty by nature, is condensed and
converted into salt in salt−pits by the heat of the sun, or else by the heat
of a fire in pans or pots or trenches. That which is made salty by
art, is also condensed by fire and changed into salt. There should be as
many salt−pits dug as the circumstance of the place permits, but there should
not be more made than can be used, although we ought to make as much
salt as we can sell. The depth of salt−pits should be moderate, and the
bottom should be level, so that all the water is evaporated from the salt by
the heat of the sun. The salt−pits should first be encrusted with salt, so
that they may not suck up the water. The method of pouring or leading
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sea−water into salt−pits is very old, and is still in use in many places. The
method is not less old, but less common, to pour well−water into salt−pits, as
was done in Babylon, for which Pliny is the authority, and in Cappadocia,
where they used not only well−water, but also spring−water. In all hot
countries salt−water and lake−water are conducted, poured or carried into
salt−pits, and, being dried by the heat of the sun, are converted into
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salt. 1 While the salt−water contained in the salt−pits is being heated by the sun,
if they be flooded with great and frequent showers of rain the evaporation is
hindered. If this happens rarely, the salt acquires a disagreeable 2 flavour, and
in this case the salt−pits have to be filled with other sweet water.
Salt from sea−water is made in the following manner. Near that part
of the seashore where there is a quiet pool, and there are wide, level plains
which the inundations of the sea do not overflow, three, four, five, or six
trenches are dug six feet wide, twelve feet deep, and six hundred feet long,
or longer if the level place extends for a longer distance; they are two hundred
feet distant from one another; between these are three transverse trenches.
Then are dug the principal pits, so that when the water has been raised from
the pool it can flow into the trenches, and from thence into the salt−pits,
of which there are numbers on the level ground between the trenches. The
salt−pits are basins dug to a moderate depth; these are banked round with
the earth which was dug in sinking them or in cleansing them, so that between
the basins, earth walls are made a foot high, which retain the water let into
them. The trenches have openings, through which the first basins receive
the water; these basins also have openings, through which the water flows
again from one into the other. There should be a slight fall, so that the
water may flow from one basin into the other, and can thus be replenished.
All these things having been done rightly and in order, the gate is raised that
opens the mouth of the pool which contains sea−water mixed with rain−water
or river−water; and thus all of the trenches are filled. Then the gates of the
first basins are opened, and thus the remaining basins are filled with the
water from the first; when this salt−water condenses, all these basins are
incrusted, and thus made clean from earthy matter. Then again the first
basins are filled up from the nearest trench with the same kind of water,
and left until much of the thin liquid is converted into vapour by the heat
of the sun and dissipated, and the remainder is considerably thickened. Then
their gates being opened, the water passes into the second basins; and
when it has remained there for a certain space of time the gates are opened,
so that it flows into the third basins, where it is all condensed into salt.
After the salt has been taken out, the basins are filled again and again with
sea−water. The salt is raked up with wooden rakes and thrown out with
shovels.
Salt−water is also boiled in pans, placed in sheds near the wells from
which it is drawn. Each shed is usually named from some animal or other
thing which is pictured on a tablet nailed to it. The walls of these sheds
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are made either from baked earth or from wicker work covered with thick
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ASEA. BPOOL. CGATE. DTRENCHES. ESALT BASINS. FRAKE.
GSHOVEL.
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mud, although some may be made of stones or bricks. When of brick they
are often sixteen feet high, and if the roof rises twenty−four feet high, then
the walls which are at the ends must be made forty feet high, as likewise
the interior partition walls. The roof consists of large shingles four feet long,
one foot wide, and two digits thick; these are fixed on long narrow planks
placed on the rafters, which are joined at the upper end and slope in opposite
directions. The whole of the under side is plastered one digit thick with
straw mixed with lute; likewise the roof on the outside is plastered one
and a half feet thick with straw mixed with lute, in order that the shed
should not run any risk of fire, and that it should be proof against rain, and
be able to retain the heat necessary for drying the lumps of salt. Each shed
is divided into three parts, in the first of which the firewood and straw are
placed; in the middle room, separated from the first room by a partition, is
the fireplace on which is placed the caldron. To the right of the caldron is
a tub, into which is emptied the brine brought into the shed by the porters;
to the left is a bench, on which there is room to lay thirty pieces of salt.
In the third room, which is in the back part of the house, there is made a pile
of clay or ashes eight feet higher than the floor, being the same height as the
bench. The master and his assistants, when they carry away the lumps of
salt from the caldrons, go from the former to the latter. They ascend from
the right side of the caldron, not by steps, but by a slope of earth. At the
top of the end wall are two small windows, and a third is in the roof, through
which the smoke escapes. This smoke, emitted from both the back and the
front of the furnace, finds outlet through a hood through which it makes
its way up to the windows; this hood consists of boards projecting one
beyond the other, which are supported by two small beams of the roof.
Opposite the fireplace the middle partition has an open door eight feet high
and four feet wide, through which there is a gentle draught which drives the
smoke into the last room; the front wall also has a door of the same height
and width. Both of these doors are large enough to permit the firewood or
straw or the brine to be carried in, and the lumps of salt to be carried out;
these doors must be closed when the wind blows, so that the boiling will
not be hindered. Indeed, glass panes which exclude the wind but transmit the
light, should be inserted in the windows in the walls.
They construct the greater part of the fireplace of rock−salt and of clay
mixed with salt and moistened with brine, for such walls are greatly
hardened by the fire. These fireplaces are made eight and a half feet long,
seven and three quarters feet wide, and, if wood is burned in them, nearly
four feet high; but if straw is burned in them, they are six feet high. An
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iron rod, about four feet long, is engaged in a hole in an iron foot, which
stands on the base of the middle of the furnace mouth. This mouth is three
feet in width, and has a door which opens inward; through it they throw
in the straw.
The caldrons are rectangular, eight feet long, seven feet wide, and half a
foot high, and are made of sheets of iron or lead, three feet long and of the
same width, all but two digits. These plates are not very thick, so that the
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ASHED. BPAINTED SIGNS. CFIRST ROOM. DMIDDLE ROOM. ETHIRD
ROOM. FTWO LITTLE WINDOWS IN THE END WALL. GTHIRD LITTLE WINDOW IN THE
ROOF. HWELL. IWELL OF ANOTHER KIND. KCASK. LPOLE. MFORKED
STICKS IN WHICH THE PORTERS REST THE POLE WHEN THEY ARE TIRED.
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water is heated more quickly by the fire, and is boiled away rapidly. The
more salty the water is, the sooner it is condensed into salt. To prevent
the brine from leaking out at the points where the metal plates are fastened
with rivets, the caldrons are smeared over with a cement made of ox−liver
and ox−blood mixed with ashes. On each side of the middle of the furnace
two rectangular posts, three feet long, and half a foot thick and wide are
set into the ground, so that they are distant from each other only one and
a half feet. Each of them rises one and a half feet above the caldron. After
the caldron has been placed on the walls of the furnace, two beams of the
same width and thickness as the posts, but four feet long, are laid on these
posts, and are mortised in so that they shall not fall. There rest trans−
versely upon these beams three bars, three feet long, three digits wide, and
two digits thick, distant from one another one foot. On each of these hang
three iron hooks, two beyond the beams and one in the middle; these are a
foot long, and are hooked at both ends, one hook turning to the right, the other
to the left. The bottom hook catches in the eye of a staple, whose ends are
fixed in the bottom of the caldron, and the eye projects from it. There are
besides, two longer bars six feet long, one palm wide, and three digits thick,
which pass under the front beam and rest upon the rear beam. At the rear end
of each of the bars there is an iron hook two feet and three digits long, the
lower end of which is bent so as to support the caldron. The rear end of the
caldron does not rest on the two rear corners of the fireplace, but is distant
from the fireplace two thirds of a foot, so that the flame and smoke can escape;
this rear end of the fireplace is half a foot thick and half a foot higher than
the caldron. This is also the thickness and height of the wall between the
caldron and the third room of the shed, to which it is adjacent. This back
wall is made of clay and ashes, unlike the others which are made of rock−salt.
The caldron rests on the two front corners and sides of the fireplace, and is
cemented with ashes, so that the flames shall not escape. If a dipperful
of brine poured into the caldron should flow into all the corners, the caldron
is rightly set upon the fireplace.
The wooden dipper holds ten Roman sextarii, and the cask holds eight
dippers full 3 . The brine drawn up from the well is poured into such casks
and carried by porters, as I have said before, into the shed and poured into a
tub, and in those places where the brine is very strong it is at once trans−
ferred with the dippers into the caldron. That brine which is less strong is
thrown into a small tub with a deep ladle, the spoon and handle of which
are hewn out of one piece of wood. In this tub rock−salt is placed in order
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AFIREPLACE. BMOUTH OF FIREPLACE. CCALDRON. DPOSTS SUNK INTO THE
GROUND. ECROSS−BEAMS. FSHORTER BARS. GIRON HOOKS. HSTAPLES.
ILONGER BARS. KIRON ROD BENT TO SUPPORT THE CALDRON.
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that the water should be made more salty, and it is then run off through a
launder which leads into the caldron. From thirty−seven dippersful of brine
the master or his deputy, at Halle in Saxony, 4 makes two cone−shaped pieces
of salt. Each master has a helper, or in the place of a helper his wife assists
him in his work, and, in addition, a youth who throws wood or straw under
the caldron. He, on account of the great heat of the workshop, wears
a straw cap on his head and a breech cloth, being otherwise quite naked.
As soon as the master has poured the first dipperful of brine into the caldron
the youth sets fire to the wood and straw laid under it. If the firewood is
bundles of faggots or brushwood, the salt will be white, but if straw is burned,
then it is not infrequently blackish, for the sparks, which are drawn up with
the smoke into the hood, fall down again into the water and colour it black.
In order to accelerate the condensation of the brine, when the master
has poured in two casks and as many dippersful of brine, he adds about a
Roman cyathus and a half of bullock' s blood, or of calf' s blood, or buck' s
blood, or else he mixes it into the nineteenth dipperful of brine, in order that
it may be dissolved and distributed into all the corners of the caldron; in other
places the blood is dissolved in beer. When the boiling water seems to be
mixed with scum, he skims it with a ladle; this scum, if he be working with
rock−salt, he throws into the opening in the furnace through which the smoke
escapes, and it is dried into rock−salt; if it be not from rock−salt, he pours
it on to the floor of the workshop. From the beginning to the boiling and
skimming is the work of half−an−hour; after this it boils down for another
quarter−of−an−hour, after which time it begins to condense into salt. When
it begins to thicken with the heat, he and his helper stir it assiduously with a
wooden spatula, and then he allows it to boil for an hour. After this he pours
in a cyathus and a half of beer. In order that the wind should not blow
into the caldron, the helper covers the front with a board seven and a half
feet long and one foot high, and covers each of the sides with boards three and
three quarters feet long. In order that the front board may hold more
firmly, it is fitted into the caldron itself, and the sideboards are fixed on the
front board and upon the transverse beam. Afterward, when the boards
have been lifted off, the helper places two baskets, two feet high and as many
wide at the top, and a palm wide at the bottom, on the transverse beams,
and into them the master throws the salt with a shovel, taking half−an−hour
to fill them. Then, replacing the boards on the caldron, he allows the brine
to boil for three quarters of an hour. Afterward the salt has again to be
removed with a shovel, and when the baskets are full, they pile up the salt in
heaps.
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In different localities the salt is moulded into different shapes. In the
baskets the salt assumes the form of a cone; it is not moulded in baskets
alone, but also in moulds into which they throw the salt, which are made in
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AWOODEN DIPPER. BCASK. CTUB. DMASTER. EYOUTH. FWIFE.
GWOODEN SPADE. HBOARDS. IBASKETS. KHOE. LRAKE. MSTRAW.
NBOWL. OBUCKET CONTAINING THE BLOOD. PTANKARD WHICH CONTAINS BEER.
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the likeness of many objects, as for instance tablets. These tablets and
cones are kept in the higher part of the third room of the house, or else on
the flat bench of the same height, in order that they may dry better in the
warm air. In the manner I have described, a master and his helper continue
one after the other, alternately boiling the brine and moulding the salt,
day and night, with the exception only of the annual feast days. No caldron
is able to stand the fire for more than half a year. The master pours in water
and washes it out every week; when it is washed out he puts straw under
it and pounds it; new caldrons he washes three times in the first two
weeks, and afterward twice. In this manner the incrustations fall from
the bottom; if they are not cleared off, the salt would have to be made
more slowly over a fiercer fire, which requires more brine and burns the
plates of the caldron. If any cracks make their appearance in the caldron
they are filled up with cement. The salt made during the first two weeks is
not so good, being usually stained by the rust at the bottom where incrusta−
tions have not yet adhered.
Although salt made in this manner is prepared only from the brine of
APOOL. BPOTS. CLADLE. DPANS. ETONGS.
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springs and wells, yet it is also possible to use this method in the case of
river−, lake−, and sea−water, and also of those waters which are artificially
salted. For in places where rock−salt is dug, the impure and the broken pieces
are thrown into fresh water, which, when boiled, condenses into salt. Some,
indeed, boil sea−salt in fresh water again, and mould the salt into the little
cones and other shapes.
Some people make salt by another method, from salt water which
flows from hot springs that issue boiling from the earth. They set earthen−
ware pots in a pool of the spring−water, and into them they pour water scooped
up with ladles from the hot spring until they are half full. The perpetual
heat of the waters of the pool evaporates the salt water just as the heat of
the fire does in the caldrons. As soon as it begins to thicken, which happens
when it has been reduced by boiling to a third or more, they seize the pots
with tongs and pour the contents into small rectangular iron pans, which have
also been placed in the pool. The interior of these pans is usually three feet
long, two feet wide, and three digits deep, and they stand on four heavy legs,
so that the water flows freely all round, but not into them. Since the water
flows continuously from the pool through the little canals, and the spring
APOTS. BTRIPOD. CDEEP LADLE.
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always provides a new and copious supply, always boiling hot, it condenses
the thickened water poured into the pans into salt; this is at once taken
out with shovels, and then the work begins all over again. If the salty water
contains other juices, as is usually the case with hot springs, no salt should
be made from them.
Others boil salt water, and especially sea−water, in large iron pots;
this salt is blackish, for in most cases they burn straw under them. Some
people boil in these pots the brine in which fish is pickled. The salt which
they make tastes and smells of fish.
ATRENCH. BVAT INTO WHICH THE SALT WATER FLOWS. CLADLE. DSMALL
BUCKET WITH POLE FASTENED INTO IT.
Those who make salt by pouring brine over firewood, lay the wood in
trenches which are twelve feet long, seven feet wide, and two and one half
feet deep, so that the water poured in should not flow out. These trenches
are constructed of rock−salt wherever it is to be had, in order that they should
not soak up the water, and so that the earth should not fall in on the front,
back and sides. As the charcoal is turned into salt at the same time as the
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ALARGE VAT. BPLUG. CSMALL TUB. DDEEP LADLE. ESMALL VAT.
FCALDRON.
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salt liquor, the Spaniards think, as Pliny writes 5 , that the wood itself turns
into salt. Oak is the best wood, as its pure ash yields salt; elsewhere hazel−
wood is lauded. But with whatever wood it be made, this salt is not
greatly appreciated, being black and not quite pure; on that account this
method of salt−making is disdained by the Germans and Spaniards.
The solutions from which salt is made are prepared from salty earth or
from earth rich in salt and saltpetre. Lye is made from the ashes of reeds
and rushes. The solution obtained from salty earth by boiling, makes salt
only; from the other, of which I will speak more a little later, salt and salt−
petre are made; and from ashes is derived lye, from which its own salt is
obtained. The ashes, as well as the earth, should first be put into a large
vat; then fresh water should be poured over the ashes or earth, and it should
be stirred for about twelve hours with a stick, so that it may dissolve the
salt. Then the plug is pulled out of the large vat; the solution of salt or the
lye is drained into a small tub and emptied with ladles into small vats;
finally, such a solution is transferred into iron or lead caldrons and boiled,
until the water having evaporated, the juices are condensed into salt. The
above are the various methods for making salt. (Illustration p. 557.)
Nítrum 6 is usually made from nitrous waters, or from solutions or from
lye. In the same manner as sea−water or salt−water is poured into salt−pits
and evaporated by the heat of the sun and changed into salt, so the nítrous
Nile is led into nítrum pits and evaporated by the heat of the sun and con−
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ANILE. BNITRUM−PITS, SUCH AS I CONJECTURE THEM TO BE. 7
verted into nítrum. Just as the sea, in flowing of its own will over the soil
of this same Egypt, is changed into salt, so also the Nile, when it overflows
in the dog days, is converted into nitrum when it flows into the nítrum pits.
The solution from which nitrum is produced is obtained from fresh water
percolating through nitrous earth, in the same manner as lye is made from
fresh water percolating through ashes of oak or hard oak. Both solutions
are taken out of vats and poured into rectangular copper caldrons, and are
boiled until at last they condense into nitrum.
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Native as well as manufactured nítrum is mixed in vats with urine
and boiled in the same caldrons; the decoction is poured into vats in which
are copper wires, and, adhering to them, it hardens and becomes chrysocolla,
which the Moors call borax. Formerly nitrum was compounded with
Cyprian verdigris, and ground with Cyprian copper in Cyprian mortars, as
Pliny writes. Some chrysocolla is made of rock−alum and sal−ammoniac. 8
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AVAT IN WHICH THE SODA IS MIXED. BCALDRON. CTUB IN WHICH chrysocolla IS
CONDENSED. DCOPPER WIRES. EMORTAR.
Saltpetre 9 is made from a dry, slightly fatty earth, which, if it be re−
tained for a while in the mouth, has an acrid and salty taste. This earth,
together with a powder, are alternately put into a vat in layers a palm deep.
The powder consists of two parts of unslaked lime and three parts of ashes of
oak, or holmoak, or Italian oak, or Turkey oak, or of some similar kind. Each
vat is filled with alternate layers of these to within three−quarters of a foot
of the top, and then water is poured in until it is full. As the water percolates
through the material it dissolves the saltpetre; then, the plug being pulled
out from the vat, the solution is drained into a tub and ladled out into small
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vats. If when tested it tastes very salty, and at the same time acrid, it is
good; but, if not, then it is condemned, and it must be made to percolate
again through the same material or through a fresh lot. Even two or three
waters may be made to percolate through the same earth and become full
of saltpetre, but the solutions thus obtained must not be mixed together
unless all have the same taste, which rarely or never happens. The first of
these solutions is poured into the first vat, the next into the second, the third
into the third vat; the second and third solutions are used instead of plain
water to percolate through fresh material; the first solution is made in
this manner from both the second and third. As soon as there is an abun−
dance of this solution it is poured into the rectangular copper caldron and
evaporated to one half by boiling; then it is transferred into a vat covered
with a lid, in which the earthy matter settles to the bottom. When the
solution is clear it is poured back into the same pan, or into another, and
re−boiled. When it bubbles and forms a scum, in order that it should
not run over and that it may be greatly purified, there is poured into it three
or four pounds of lye, made from three parts of oak or similar ash and one of
unslaked lime. But in the water, prior to its being poured in, is dissolved rock−
alum, in the proportion of one hundred and twenty librae of the former to five
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librae of the latter. Shortly afterward the solution will be found to be clear
and blue. It is boiled until the waters, which are easily volatile ( subtiles ), are
evaporated, and then the greater part of the salt, after it has settled at the
bottom of the pan, is taken out with iron ladles. Then the concentrated
solution is transferred to the vat in which rods are placed horizontally and
vertically, to which it adheres when cold, and if there be much, it is condensed
in three or four days into saltpetre. Then the solution which has not con−
gealed, is poured out and put on one side or re−boiled. The saltpetre being
cut out and washed with its own solution, is thrown on to boards that it may
drain and dry. The yield of saltpetre will be much or little in proportion
to whether the solution has absorbed much or little; when the saltpetre
has been obtained from lye, which purifies itself, it is somewhat clear and
pure.
The purest and most transparent, because free from salt, is made if it is
drawn off at the thickening stage, according to the following method. There
ACALDRON. BLARGE VAT INTO WHICH SAND IS THROWN. CPLUG. DTUB.
EVAT CONTAINING THE RODS.
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are poured into the caldron the same number of amphorae of the solution as of
congíi of the lye of which I have already spoken, and into the same caldron
is thrown as much of the already made saltpetre as the solution and lye will
dissolve. As soon as the mixture effervesces and forms scum, it is trans−
ferred to a vat, into which on a cloth has been thrown washed sand obtained
from a river. Soon afterward the plug is drawn out of the hole at the
bottom, and the mixture, having percolated through the sand, escapes into
a tub. It is then reduced by boiling in one or another of the caldrons, until
the greater part of the solution has evaporated; but as soon as it is well
boiled and forms scum, a little lye is poured into it. Then it is transferred to
another vat in which there are small rods, to which it adheres and congeals in
two days if there is but little of it, or if there is much in three days, or
at the most in four days; if it does not condense, it is poured back into the
caldron and re−boiled down to half; then it is transferred to the vat to cool.
The process must be repeated as often as is necessary.
Others refine saltpetre by another method, for with it they fill a pot
made of copper, and, covering it with a copper lid, set it over live coals, where
it is heated until it melts. They do not cement down the lid, but it has
a handle, and can be lifted for them to see whether or not the melting has taken
place. When it has melted, powdered sulphur is sprinkled in, and if the pot
set on the fire does not light it, the sulphur kindles, whereby the thick, greasy
matter floating on the saltpetre burns up, and when it is consumed the salt−
petre is pure. Soon afterward the pot is removed from the fire, and later, when
cold, the purest saltpetre is taken out, which has the appearance of white
marble, the earthy residue then remains at the bottom. The earths from
which the solution was made, together with branches of oak or similar trees,
are exposed under the open sky and sprinkled with water containing saltpetre.
After remaining thus for five or six years, they are again ready to be made
into a solution.
Pure saltpetre which has rested many years in the earth, and that which
exudes from the stone walls of wine cellars and dark places, is mixed with the
first solution and evaporated by boiling.
Thus far I have described the methods of making nítrum, which are not
less varied or multifarious than those for making salt. Now I propose to
describe the methods of making alum, 10 which are likewise neither all alike,
nor simple, because it is made from boiling aluminous water until it con−
denses to alum, or else from boiling a solution of alum which is obtained
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from a kind of earth, or from rocks, or from pyrites, or other minerals.
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This kind of earth having first been dug up in such quantity as would
make three hundred wheelbarrow loads, is thrown into two tanks; then the
water is turned into them, and if it (the earth) contains vitriol it must be
diluted with urine. The workmen must many times a day stir the
ore with long, thick sticks in order that the water and urine may be
mixed with it; then the plugs having been taken out of both tanks, the
solution is drawn off into a trough, which is carved out of one or two trees.
If the locality is supplied with an abundance of such ore, it should not
immediately be thrown into the tanks, but first conveyed into open spaces
and heaped up, for the longer it is exposed to the air and the rain, the better it
is; after some months, during which the ore has been heaped up in open
spaces into mounds, there are generated veinlets of far better quality than
the ore. Then it is conveyed into six or more tanks, nine feet in length
and breadth and five in depth, and afterward water is drawn into them
of similar solution. After this, when the water has absorbed the alum, the
plugs are pulled out, and the solution escapes into a round reservoir forty
feet wide and three feet deep. Then the ore is thrown out of the tanks
into other tanks, and water again being run into the latter and the urine
added and stirred by means of poles, the plugs are withdrawn and
the solution is run off into the same reservoir. A few days afterward,
the reservoirs containing the solution are emptied through a small launder,
and run into rectangular lead caldrons; it is boiled in them until the
1
773
greater part of the water has evaporated. The earthy sediment deposited
at the bottom of the caldron is composed of fatty and aluminous matter, which
usually consists of small incrustations, in which there is not infrequently found
a very white and very light powder of asbestos or gypsum. The solution now
seems to be full of meal. Some people instead pour the partly evaporated
solution into a vat, so that it may become pure and clear; then pouring it
back into the caldron, they boil it again until it becomes mealy. By which−
ever process it has been condensed, it is then poured into a wooden tub
sunk into the earth in order to cool it. When it becomes cold it is poured
into vats, in which are arranged horizontal and vertical twigs, to which the
alum clings when it condenses; and thus are made the small white trans−
parent cubes, which are laid to dry in hot rooms.
If vitriol forms part of the aluminous ore, the material is dissolved in
water without being mixed with urine, but it is necessary to pour that into
the clear and pure solution when it is to be re−boiled. This separates the
vitriol from the alum, for by this method the latter sinks to the bottom of the
caldron, while the former floats on the top; both must be poured separately
into smaller vessels, and from these into vats to condense. If, however, when
the solution was re−boiled they did not separate, then they must be poured
from the smaller vessels into larger vessels and covered over; then the vitriol
separating from the alum, it condenses. Both are cut out and put to dry in
the hot room, and are ready to be sold; the solution which did not congeal in
1
774
ATANKS. BSTIRRING POLES. CPLUG. DTROUGH. ERESERVOIR. FLAUNDER.
GLEAD CALDRON. HWOODEN TUBS SUNK INTO THE EARTH. IVATS IN WHICH
TWIGS ARE FIXED.
1
775
the vessels and vats is again poured back into the caldron to be re−boiled.
The earth which settled at the bottom of the caldron is carried back to the
tanks, and, together with the ore, is again dissolved with water and urine.
The earth which remains in the tanks after the solution has been drawn off
is emptied in a heap, and daily becomes more and more aluminous in the
same way as the earth from which saltpetre was made, but fuller of its juices,
wherefore it is again thrown into the tanks and percolated by water.
Aluminous rock is first roasted in a furnace similar to a lime kiln. At
the bottom of the kiln a vaulted fireplace is made of the same kind of rock;
the remainder of the empty part of the kiln is then entirely filled with the
same aluminous rocks. Then they are heated with fire until they are red
hot and have exhaled their sulphurous fumes, which occurs, according to their
divers nature, within the space of ten, eleven, twelve, or more hours. One
thing the master must guard against most of all is not to roast the rock
either too much or too little, for on the one hand they would not soften when
sprinkled with water, and on the other they either would be too hard or
would crumble into ashes; from neither would much alum be obtained, for
the strength which they have would be decreased. When the rocks are cooled
they are drawn out and conveyed into an open space, where they are piled one
upon the other in heaps fifty feet long, eight feet wide, and four feet high,
which are sprinkled for forty days with water carried in deep ladles. In
spring the sprinkling is done both morning and evening, and in summer at
1
776
noon besides. After being moistened for this length of time the rocks begin
to fall to pieces like slaked lime, and there originates a certain new material
of the future alum, which is soft and similar to the liquidae medullae found
in the rocks. It is white if the stone was white before it was roasted, and
rose−coloured if red was mixed with the white; from the former, white
alum is obtained, and from the latter, rose−coloured. A round furnace is
made, the lower part of which, in order to be able to endure the force of
the heat, is made of rock that neither melts nor crumbles to powder by the
fire. It is constructed in the form of a basket, the walls of which are two
feet high, made of the same rock. On these walls rests a large round caldron
made of copper plates, which is concave at the bottom, where it is eight feet
in diameter. In the empty space under the bottom they place the wood to be
kindled with fire. Around the edge of the bottom of the caldron, rock
is built in cone−shaped, and the diameter of the bottom of the rock structure
is seven feet, and of the top ten feet; it is eight feet deep. The inside,
after being rubbed over with oil, is covered with cement, so that it may be
able to hold boiling water; the cement is composed of fresh lime, of
which the lumps are slaked with wine, of iron−scales, and of sea−snails,
ground and mixed with the white of eggs and oil. The edges of the caldron
are surmounted with a circle of wood a foot thick and half a foot high,
on which the workmen rest the wooden shovels with which they cleanse
the water of earth and of the undissolved lumps of rock that remain at
1
777
the bottom of the caldron. The caldron, being thus prepared, is entirely
filled through a launder with water, and this is boiled with a fierce fire
until it bubbles. Then little by little eight wheelbarrow loads of the
material, composed of roasted rock moistened with water, are gradually
emptied into the caldron by four workmen, who, with their shovels which
reach to the bottom, keep the material stirred and mixed with water, and
by the same means they lift the lumps of undissolved rock out of the
caldron. In this manner the material is thrown in, in three or four lots, at
intervals of two or three hours more or less; during these intervals, the
water, which has been cooled by the rock and material, again begins to boil.
The water, when sufficiently purified and ready to congeal, is ladled out and
run off with launders into thirty troughs. These troughs are made of oak,
holm oak, or Turkey oak; their interior is six feet long, five feet deep, and
four feet wide. In these the water congeals and condenses into alum, in the
spring in the space of four days, and in summer in six days. Afterward the
holes at the bottom of the oak troughs being opened, the water which has
not congealed is drawn off into buckets and poured back into the caldron;
or it may be preserved in empty troughs, so that the master of the workmen,
having seen it, may order his helpers to pour it into the caldron, for the water
which is not altogether wanting in alum, is considered better than that which
has none at all. Then the alum is hewn out with a knife or a chisel. It is
thick and excellent according to the strength of the rock, either white or
pink according to the colour of the rock. The earthy powder, which remains
three to four digits thick as the residue of the alum at the bottom of the
trough is again thrown into the caldron and boiled with fresh aluminous
material. Lastly, the alum cut out is washed, and dried, and sold.
Alum is also made from crude pyrites and other aluminous mixtures.
It is first roasted in an enclosed area: then, after being exposed for some
1
778
AFURNACE. BENCLOSED SPACE. CALUMINOUS ROCK. DDEEP LADLE.
ECALDRON. FLAUNDER. GTROUGHS.
1
779
months to the air in order to soften it, it is thrown into vats and dissolved.
After this the solution is poured into the leaden rectangular pans and boiled
until it condenses into alum. The pyrites and other stones which are not
mixed with alum alone, but which also contain vitriol, as is most usually the
case, are both treated in the manner which I have already described. Finally,
if metal is contained in the pyrites and other rock, this material must be dried,
and from it either gold, silver, or copper is made in a furnace.
Vitriol 11 can be made by four different methods; by two of these methods
1
780
from water containing vitriol; by one method from a solution of melantería,
sory and chalcítís; and by another method from earth or stones mixed with
vitriol.
The vitriol water is collected into pools, and if it cannot be drained into
them, it must be drawn up and carried to them in buckets by a workman.
1
781
ATUNNEL. BBUCKET. CPIT.
In hot regions or in summer, it is poured into out−of−door pits which have
been dug to a certain depth, or else it is extracted from shafts by pumps
and poured into launders, through which it flows into the pits, where it is
condensed by the heat of the sun. In cold regions and in winter these vitriol
waters are boiled down with equal parts of fresh water in rectangular leaden
caldrons; then, when cold, the mixture is poured into vats or into tanks,
which Pliny calls wooden fish−tanks. In these tanks light cross−beams are
fixed to the upper part, so that they may be stationary, and from them hang
ropes stretched with little stones; to these the contents of the thickened
solutions congeal and adhere in transparent cubes or seeds of vitriol, like
bunches of grapes.
1
782
ACALDRON. BTANK. CCROSS−BARS. DROPES. ELITTLE STONES.
By the third method vitriol is made out of melanteria and sory. If
the mines give an abundant supply of melanteria and sory, it is better to
reject the chalcítís, and especially the mísy, for from these the vitriol is impure,
particularly from the misy. These materials having been dug and thrown
into the tanks, they are first dissolved with water; then, in order to recover
the pyrites from which copper is not rarely smelted and which forms a sedi−
ment at the bottom of the tanks, the solution is transferred to other vats,
which are nine feet wide and three feet deep. Twigs and wood which float
on the surface are lifted out with a broom made of twigs, and afterward all the
sediment settles at the bottom of this vat. The solution is poured into a
rectangular leaden caldron eight feet long, three feet wide, and the same in
depth. In this caldron it is boiled until it becomes thick and viscous, when
it is poured into a launder, through which it runs into another leaden caldron
of the same size as the one described before. When cold, the solution is
drawn off through twelve little launders, out of which it flows into as many
wooden tubs four and a half feet deep and three feet wide. Upon these tubs
are placed perforated crossbars distant from each other from four to six
digits, and from the holes hang thin laths, which reach to the bottom, with
1
783
pegs or wedges driven into them. The vitriol adheres to these laths, and
within the space of a few days congeals into cubes, which are taken away
and put into a chamber having a sloping board floor, so that the moisture
which drips from the vitriol may flow into a tub beneath. This solution is
re−boiled, as is also that solution which was left in the twelve tubs, for, by
reason of its having become too thin and liquid, it did not congeal, and was
thus not converted into vitriol.
AWOODEN TUB. BCROSS−BARS. CLATHS. DSLOPING FLOOR OF THE CHAMBER.
ETUB PLACED UNDER IT.
The fourth method of making vitriol is from vitriolous earth or stones.
Such ore is at first carried and heaped up, and is then left for five or six months
exposed to the rain of spring and autumn, to the heat of summer, and to the
rime and frost of winter. It must be turned over several times with shovels,
so that the part at the bottom may be brought to the top, and it is thus
ventilated and cooled; by this means the earth crumbles up and loosens,
and the stone changes from hard to soft. Then the ore is covered with a roof,
or else it is taken away and placed under a roof, and remains in that place
six, seven, or eight months. Afterward as large a portion as is required is
thrown into a vat, which is half−filled with water; this vat is one hundred
1
784
feet long, twenty−four feet wide, eight feet deep. It has an opening at the
bottom, so that when it is opened the dregs of the ore from which the vitriol
comes may be drawn off, and it has, at the height of one foot from the bottom,
three or four little holes, so that, when closed, the water may be retained,
and when opened the solution flows out. Thus the ore is mixed with water,
stirred with poles and left in the tank until the earthy portions sink to the
bottom and the water absorbs the juices. Then the little holes are opened,
the solution flows out of the vat, and is caught in a vat below it; this vat is
of the same length as the other, but twelve feet wide and four feet deep. If
the solution is not sufficiently vitriolous it is mixed with fresh ore; but if it
contains enough vitriol, and yet has not exhausted all of the ore rich in vitriol,
it is well to dissolve the ore again with fresh water. As soon as the solution
becomes clear, it is poured into the rectangular leaden caldron through
launders, and is boiled until the water is evaporated. Afterward as many thin
strips of iron as the nature of the solution requires, are thrown in, and then
it is boiled again until it is thick enough, when cold, to congeal into vitriol.
Then it is poured into tanks or vats, or any other receptacle, in which all of it
that is apt to congeal does so within two or three days. The solution which
does not congeal is either poured back into the caldron to be boiled again, or
ACALDRON. BMOULDS. CCAKES
1
785
it is put aside for dissolving the new ore, for it is far preferable to fresh water.
The solidified vitriol is hewn out, and having once more been thrown into the
caldron, is re−heated until it liquefies; when liquid, it is poured into
moulds that it may be made into cakes. If the solution first poured out is
not satisfactorily thickened, it is condensed two or three times, and each
time liquefied in the caldron and re−poured into the moulds, in which
manner pure cakes, beautiful to look at, are made from it.
The vitriolous pyrites, which are to be numbered among the mixtures
( mistura ), are roasted as in the case of alum, and dissolved with water, and
the solution is boiled in leaden caldrons until it condenses into vitriol. Both
alum and vitriol are often made out of these, and it is no wonder, for these
juices are cognate, and only differ in the one point,that the former is less, the
latter more, earthy. That pyrites which contains metal must be smelted in the
furnace. In the same manner, from other mixtures of vitriolic and metallifer−
ous material are made vitriol and metal. Indeed, if ores of vitriolous pyrites
abound, the miners split small logs down the centre and cut them off in lengths
as long as the drifts and tunnels are wide, in which they lay them down trans−
versely; but, that they may be stable, they are laid on the ground with the wide
side down and the round side up, and they touch each other at the bottom,
but not at the top. The intermediate space is filled with pyrites, and the same
crushed are scattered over the wood, so that, coming in or going out, the
road is flat and even. Since the drifts or tunnels drip with water, these
pyrites are soaked, and from them are freed the vitriol and cognate things. If
the water ceases to drip, these dry and harden, and then they are raised
from the shafts, together with the pyrites not yet dissolved in the water, or
they are carried out from the tunnels; then they are thrown into vats or
tanks, and boiling water having been poured over them, the vitriol is freed
and the pyrites are dissolved. This green solution is transferred to other vats
or tanks, that it may be made clear and pure; it is then boiled in the lead
caldrons until it thickens; afterward it is poured into wooden tubs, where
it condenses on rods, or reeds, or twigs, into green vitriol.
Sulphur is made from sulphurous waters, from sulphurous ores, and
from sulphurous mixtures. These waters are poured into the leaden caldrons
and boiled until they condense into sulphur. From this latter, heated
together with iron−scales, and transferred into pots, which are afterward
covered with lute and refined sulphur, another sulphur is made, which we
call caballinum. 12
1
786
The ores 13 which consist mostly of sulphur and of earth, and rarely of
other minerals, are melted in big−bellied earthenware pots. The furnaces,
1
787
APOTS HAVING SPOUTS. BPOTS WITHOUT SPOUTS. CLIDS.
which hold two of these pots, are divided into three parts; the lowest part is a
foot high, and has an opening at the front for the draught; the top of this is
covered with iron plates, which are perforated near the edges, and these
support iron rods, upon which the firewood is placed. The middle part of the
furnace is one and a half feet high, and has a mouth in front, so that the wood
may be inserted; the top of this has rods, upon which the bottom of the pots
stand. The upper part is about two feet high, and the pots are also two feet
high and one digit thick; these have below their mouths a long, slender spout.
In order that the mouth of the pot may be covered, an earthenware lid is
made which fits into it. For every two of these pots there must be one pot
1
788
of the same size and shape, and without a spout, but having three holes, two of
which are below the mouth and receive the spouts of the two first pots; the
third hole is on the opposite side at the bottom, and through it the sulphur
flows out. In each furnace are placed two pots with spouts, and the furnace
must be covered by plates of iron smeared over with lute two digits thick; it is
thus entirely closed in, but for two or three ventholes through which the mouths
of the pots project. Outside of the furnace, against one side, is placed the pot
without a spout, into the two holes of which the two spouts of the other pots
penetrate, and this pot should be built in at both sides to keep it steady. When
the sulphur ore has been placed in the pots, and these placed in the furnace,
they are closely covered, and it is desirable to smear the joint over with lute,
so that the sulphur will not exhale, and for the same reason the pot below is
covered with a lid, which is also smeared with lute. The wood having been
kindled, the ores are heated until the sulphur is exhaled, and the vapour,
arising through the spout, penetrates into the lower pot and thickens into
sulphur, which falls to the bottom like melted wax. It then flows out
through the hole, which, as I said, is at the bottom of this pot; and the work−
man makes it into cakes, or thin sticks or thin pieces of wood are dipped in it.
Then he takes the burning wood and glowing charcoal from the furnace, and
when it has cooled, he opens the two pots, empties the residues, which, if the
ores were composed of sulphur and earth, resemble naturally extinguished
ashes; but if the ores consisted of sulphur and earth and stone, or sulphur
and stone only, they resemble earth completely dried or stones well roasted.
Afterward the pots are re−filled with ore, and the whole work is repeated.
The sulphurous mixture, whether it consists of stone and sulphur only,
or of stone and sulphur and metal, may be heated in similar pots, but with
perforated bottoms. Before the furnace is constructed, against the "second"
wall of the works two lateral partitions are built seven feet high, three feet
long, one and a half feet thick, and these are distant from each other twenty−
seven feet. Between them are seven low brick walls, that measure but
two feet and the same number of digits in height, and, like the other walls,
are three feet long and one foot thick; these little walls are at equal
distances from one another, consequently they will be two and one half feet
apart. At the top, iron bars are fixed into them, which sustain iron plates
three feet long and wide and one digit thick, so that they can bear not only
the weight of the pots, but also the fierceness of the fire. These plates have
in the middle a round hole one and a half digits wide; there must not be
more than eight of these, and upon them as many pots are placed. These
pots are perforated at the bottom, and the same number of whole pots are
1
789
placed underneath them; the former contain the mixture, and are covered
with lids; the latter contain water, and their mouths are under the holes
in the plates. After wood has been arranged round the upper pots and
ignited, the mixture being heated, red, yellow, or green sulphur drips
from it and flows down through the hole, and is caught by the pots placed
underneath the plates, and is at once cooled by the water. If the mixture
contains metal, it is reserved for smelting, and, if not, it is thrown away.
1
790
ALONG WALL. BHIGH WALLS. CLOW WALLS. DPLATES. EUPPER POTS.
FLOWER POTS.
The sulphur from such a mixture can best be extracted if the upper pots are
placed in a vaulted furnace, like those which I described among other
metallurgical subjects in Book VIII., which has no floor, but a grate inside;
under this the lower pots are placed in the same manner, but the plates
must have larger holes.
Others bury a pot in the ground, and place over it another pot with a
hole at the bottom, in which pyrites or cadmia, or other sulphurous stones
are so enclosed that the sulphur cannot exhale. A fierce fire heats the
sulphur, and it drips away and flows down into the lower pot, which contains
water. (Illustration p. 582).
Bitumen 14 is made from bituminous waters, from liquid bitumen, and
from mixtures of bituminous substances. The water, bituminous as well as
1
791
ALOWER POT. BUPPER POT. CLID.
salty, at Babylon, as Pliny writes, was taken from the wells to the salt works
and heated by the great heat of the sun, and condensed partly into liquid
bitumen and partly into salt. The bitumen being lighter, floats on the top,
while the salt being heavier, sinks to the bottom. Liquid bitumen, if there
is much floating on springs, streams and rivers, is drawn up in buckets or
other vessels; but, if there is little, it is collected with goose wings, pieces
1
792
ABITUMINOUS SPRING. BBUCKET. CPOT. DLID.
of linen, ralla, shreds of reeds, and other things to which it easily adheres,
and it is boiled in large brass or iron pots by fire and condensed. As this
bitumen is put to divers uses, some mix pitch with the liquid, others old
cart−grease, in order to temper its viscosity; these, however long they are
1
793
boiled in the pots, cannot be made hard. The mixtures containing bitumen
are also treated in the same manner as those containing sulphur, in pots
having a hole in the bottom, and it is rare that such bitumen is not highly
esteemed.
Since all solidified juices and earths, if abundantly and copiously mixed
with the water, are deposited in the beds of springs, streams or rivers, and the
stones therein are coated by them, they do not require the heat of the sun or
fire to harden them. This having been pondered over by wise men, they dis−
covered methods by which the remainder of these solidified juices and unusual
earths can be collected. Such waters, whether flowing from springs or
tunnels, are collected in many wooden tubs or tanks arranged in consecutive
order, and deposit in them such juices or earths; these being scraped off
every year, are collected, as chrysocolla 15 in the Carpathians and as ochre in
the Harz.
There remains glass, the preparation of which belongs here, for the
reason that it is obtained by the power of fire and subtle art from certain
solidified juices and from coarse or fine sand. It is transparent, as are certain
solidified juices, gems, and stones; and can be melted like fusible stones and
metals. First I must speak of the materials from which glass is made;
then of the furnaces in which it is melted; then of the methods by which it
is produced.
It is made from fusible stones and from solidified juices, or from other
juicy substances which are connected by a natural relationship. Stones
which are fusible, if they are white and translucent, are more excellent than
1
794
AMOUTH OF THE TUNNEL. BTROUGH. CTANKS. DLITTLE TROUGH.
the others, for which reason crystals take the first place. From these, when
pounded, the most excellent transparent glass was made in India, with which
no other could be compared, as Pliny relates. The second place is accorded
to stones which, although not so hard as crystal, are yet just as white and
transparent. The third is given to white stones, which are not transparent.
It is necessary, however, first of all to heat all these, and afterward they are
subjected to the pestle in order to break and crush them into coarse sand,
and then they are passed through a sieve. If this kind of coarse or fine sand
is found by the glass−makers near the mouth of a river, it saves them much
labour in burning and crushing. As regards the solidified juices, the first
place is given to soda; the second to white and translucent rock−salt; the third
to salts which are made from lye, from the ashes of the musk ivy, or from
other salty herbs. Yet there are some who give to this latter, and not to the
former, the second place. One part of coarse or fine sand made from fusible
stones should be mixed with two parts of soda or of rock−salt or of herb
salts, to which are added minute particles of magnes. 16 It is true that in our
1
795
day, as much as in ancient times, there exists the belief in the singular
power of the latter to attract to itself the vitreous liquid just as it does iron,
and by attracting it to purify and transform green or yellow into white; and
afterward fire consumes the magnes. When the said juices are not to be had,
two parts of the ashes of oak or holmoak, or of hard oak or Turkey oak,
or if these be not available, of beech or pine, are mixed with one part
of coarse or fine sand, and a small quantity of salt is added, made from salt
water or sea−water, and a small particle of magnes; but these make a less
white and translucent glass. The ashes should be made from old trees, of
which the trunk at a height of six feet is hollowed out and fire is put in, and
thus the whole tree is consumed and converted into ashes. This is done in
winter when the snow lies long, or in summer when it does not rain, for the
showers at other times of the year, by mixing the ashes with earth, render
them impure; for this reason, at such times, these same trees are cut up
into many pieces and burned under cover, and are thus converted into ashes.
Some glass−makers use three furnaces, others two, others only one.
Those who use three, melt the material in the first, re−melt it in the second,
1
796
ALOWER CHAMBER OF THE FIRST FURNACE. BUPPER CHAMBER. CVITREOUS MASS.
and in the third they cool the glowing glass vessels and other articles. Of
these the first furnace must be vaulted and similar to an oven. In the upper
chamber, which is six feet long, four feet wide, and two feet high, the
mixed materials are heated by a fierce fire of dry wood until they melt
and are converted into a vitreous mass. And if they are not satisfactorily
purified from dross, they are taken out and cooled and broken into pieces;
and the vitreous pieces are heated in pots in the same furnace.
The second furnace is round, ten feet in diameter and eight feet high,
and on the outside, so that it may be stronger, it is encompassed by five
arches, one and one half feet thick; it consists in like manner of two
chambers, of which the lower one is vaulted and is one and one half feet thick.
In front this chamber has a narrow mouth, through which the wood
can be put into the hearth, which is on the ground. At the top and in the
middle of its vault, there is a large round hole which opens to the upper
chamber, so that the flames can penetrate into it. Between the arches in
the walls of the upper chamber are eight windows, so large that the big−
bellied pots may be placed through them on to the floor of the chamber,
around the large hole. The thickness of these pots is about two digits, their
height the same number of feet, and the diameter of the belly one and a half
1
797
feet, and of the mouth and bottom one foot. In the back part of the furnace
is a rectangular hole, measuring in height and width a palm, through which
the heat penetrates into a third furnace which adjoins it.
This third furnace is rectangular, eight feet long and six feet wide; it
also consists of two chambers, of which the lower has a mouth in front, so that
firewood may be placed on the hearth which is on the ground. On each side of
this opening in the wall of the lower chamber is a recess for oblong earthen−
ware receptacles, which are about four feet long, two feet high, and one and
a half feet wide. The upper chamber has two holes, one on the right side,
the other on the left, of such height and width that earthenware receptacles
may be conveniently placed in them. These latter receptacles are three
feet long, one and a half feet high, the lower part one foot wide, and the
upper part rounded. In these receptacles the glass articles, which have been
blown, are placed so that they may cool in a milder temperature; if they were
not cooled slowly they would burst asunder. When the vessels are taken
from the upper chamber, they are immediately placed in the receptacles
to cool.
AARCHES OF THE SECOND FURNACE. BMOUTH OF THE LOWER CHAMBER.
CWINDOWS OF THE UPPER CHAMBER. DBIG−BELLIED POTS. EMOUTH OF THE
THIRD FURNACE. FRECESSES FOR THE RECEPTACLES. GOPENINGS IN THE UPPER
CHAMBER. HOBLONG RECEPTACLES.
1
798
ALOWER CHAMBER OF THE OTHER SECOND FURNACE. BMIDDLE ONE. CUPPER ONE.
DITS OPENING. EROUND OPENING. FRECTANGULAR OPENING.
1
799
Some who use two furnaces partly melt the mixture in the first, and
not only re−melt it in the second, but also replace the glass articles there.
Others partly melt and re−melt the material in different chambers of the
second furnace. Thus the former lack the third furnace, and the latter,
the first. But this kind of second furnace differs from the other second
furnace, for it is, indeed, round, but the interior is eight feet in diameter
and twelve feet high, and it consists of three chambers, of which the lowest is
not unlike the lowest of the other second furnace. In the middle chamber
wall there are six arched openings, in which are placed the pots to be heated,
and the remainder of the small windows are blocked up with lute. In the
middle top of the middle chamber is a square opening a palm in length
and width. Through this the heat penetrates into the upper chamber,
of which the rear part has an opening to receive the oblong earthenware
receptacles, in which are placed the glass articles to be slowly cooled. On
this side, the ground of the workshop is higher, or else a bench is placed there,
so that the glass−makers may stand upon it to stow away their products
more conveniently.
Those who lack the first furnace in the evening, when they have accom−
plished their day' s work, place the material in the pots, so that the heat during
the night may melt it and turn it into glass. Two boys alternately, during
night and day, keep up the fire by throwing dry wood on to the hearth. Those
who have but one furnace use the second sort, made with three chambers.
Then in the evening they pour the material into the pots, and in the morning,
having extracted the fused material, they make the glass objects, which they
place in the upper chamber, as do the others.
The second furnace consists either of two or three chambers, the first of
which is made of unburnt bricks dried in the sun. These bricks are made of a
kind of clay that cannot be easily melted by fire nor resolved into powder;
this clay is cleaned of small stones and beaten with rods. The bricks are
laid with the same kind of clay instead of lime. From the same clay the
potters also make their vessels and pots, which they dry in the shade. These
two parts having been completed, there remains the third.
The vitreous mass having been made in the first furnace in the manner
I described, is broken up, and the assistant heats the second furnace, in order
that the fragments may be re−melted. In the meantime, while they are doing
this, the pots are first warmed by a slow fire in the first furnace, so that the
vapours may evaporate, and then by a fiercer fire, so that they become red
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in drying. Afterward the glass−makers open the mouth of the furnace, and,
seizing the pots with tongs, if they have not cracked and fallen to pieces,
quickly place them in the second furnace, and they fill them up with the
fragments of the heated vitreous mass or with glass. Afterward they close
up all the windows with lute and bricks, with the exception that in each
there are two little windows left free; through one of these they inspect the
glass contained in the pot, and take it up by means of a blow−pipe; in the
other they rest another blow−pipe, so that it may get warm. Whether it
is made of brass, bronze, or iron, the blow−pipe must be three feet long.
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ABLOW−PIPE. BLITTLE WINDOW. CMARBLE. DFORCEPS. EMOULDS BY
MEANS OF WHICH THE SHAPES ARE PRODUCED.
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In front of the window is inserted a lip of marble, on which rests the
heaped−up clay and the iron shield. The clay holds the blow−pipe when it
is put into the furnace, whereas the shield preserves the eyes of the glass−maker
from the fire. All this having been carried out in order, the glass−makers
bring the work to completion. The broken pieces they re−melt with dry wood,
which emits no smoke, but only a flame. The longer they re−melt it, the purer
and more transparent it becomes, the fewer spots and blisters there are, and
therefore the glass−makers can carry out their work more easily. For this
reason those who only melt the material from which glass is made for one
night, and then immediately make it up into glass articles, make them less
pure and transparent than those who first produce a vitreous mass and then
re−melt the broken pieces again for a day and a night. And, again, these make
a less pure and transparent glass than do those who melt it again for two days
and two nights, for the excellence of the glass does not consist solely in the
material from which it is made, but also in the melting. The glass−makers
often test the glass by drawing it up with the blowpipes; as soon as they
observe that the fragments have been re−melted and purified satisfactorily,
each of them with another blow−pipe which is in the pot, slowly stirs and takes
up the glass which sticks to it in the shape of a ball like a glutinous, coagulated
gum. He takes up just as much as he needs to complete the article he wishes
to make; then he presses it against the lip of marble and kneads it round and
round until it consolidates. When he blows through the pipe he blows as
he would if inflating a bubble; he blows into the blow−pipe as often as it is
necessary, removing it from his mouth to re−fill his cheeks, so that his breath
does not draw the flames into his mouth. Then, twisting the lifted blow−pipe
round his head in a circle, he makes a long glass, or moulds the same in a
hollow copper mould, turning it round and round, then warming it again,
blowing it and pressing it, he widens it into the shape of a cup or vessel, or of
any other object he has in mind. Then he again presses this against the
marble to flatten the bottom, which he moulds in the interior with his other
blow−pipe. Afterward he cuts out the lip with shears, and, if necessary, adds
feet and handles. If it so please him, he gilds it and paints it with various
colours. Finally, he lays it in the oblong earthenware receptacle, which is
placed in the third furnace, or in the upper chamber of the second furnace,
that it may cool. When this receptacle is full of other slowly−cooled articles,
he passes a wide iron bar under it, and, carrying it on the left arm, places it
in another recess.
The glass−makers make divers things, such as goblets, cups, ewers, flasks,
dishes, plates, panes of glass, animals, trees, and ships, all of which excellent and
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wonderful works I have seen when I spent two whole years in Venice some
time ago. Especially at the time of the Feast of the Ascension they were on
sale at Morano, where are located the most celebrated glass−works. These I
saw on other occasions, and when, for a certain reason, I visited Andrea
Naugerio in his house which he had there, and conversed with him and
Francisco Asulano.
END OF BOOK XII