Of cleaning pi&urcs and paintings.
THE art of cleaning pictures and paint-J[ ings is of great consequence to the preserving valuable works of that kind : but has been very little understood even by those ho profess to practise it ; on which account many very valuable pictures have been damaged : and indeed few escape without damage, in a greater or less degree, which come under the hands of those who pretend to make it their business ; and yet most generally know no other than one single way of treating all the subjects they are to operate upon, however different
serent may be the condition or circumstances of them.
As a painting may be, however, fouled with a variety of different kinds of matter, many of which will not be dissolved, or suffer their tex ture to be destroyed by the fame substances, it is necessary- to know what will dissolve or cor rode each such kind ; for there is no other means of removing, or taking off any foulness, than by dissolving or corroding by some proper menstruum the matter which constitutes it ; except by actual .violence ; which the ten der nature of oil paintings by no means suffers
them to bear. Of these substances, which will remove, by dissolving or corroding it, the matter which may foul paintings, some are very apt, likewise, to act upon and dissolve the oil in the painting itself ; and consequently to disor der or bring off the colours ; while others are, on the contrary, passive and innocent, with respect to the painting ; and may be used freely, or indeed in any quantity whatever, without the least inconvenience of this kind.
As paintings to be cleaned are likewise var nished with a variety of substances of different natures, which sometimes require to be taken off, and at other times are much better left re maining, it is very necessary to be able to judge what is best to be done in this point ; as like wise to know the means by which each fort qf
varnish may be taken off without injury to the painting : for in fact, without this, there is no way qf cleaning pictures in some circumstances ; but by scouring till, as well the furlace of the picture, as the foulness, be cleared away. I shall therefore first give some account of the nature of the substances, which are, or may be used for cleaning paintings in oil, as it regards this application of them; and then shew, how they may be used as well for the taking off the varnish ; as the removing any foulness, that may lie either upon or under it.
The first, and most general substance used for cleaning pictures, is water. This will remove many kinds of glutinous bodies, and foulness arising from them ; such as sugar, honey, glue, and many others, and also take off any varnish of gum Arabic, glair of eggs, and isinglass ; and is therefore the greatest in strument in this work. It may be used with out any caution with regard to the colours ; .as it will not, in the least, affect the oil which holds them together.
Olive oil, or butter, though not applied to this purpose, through an ignorance of their , efficacy, will remove many of those spots or foulness which resist even sope ; as they will dissolve or corrode pitch, resin, and other bodies of a like kind, that otherwise require spirit of wine and oil of turpentine, which en danger the painting : and they may be used very freely, not having the least effect on the oil of the painting.
Wood-ashes, or what will better answer the purpose, when used in a proper proportion, pearl-ashes, being melted in water, make a proper dissolvent for most kinds of matter which foul paintings : but they must be used with great discretion, as they will touch or corrode the oil of the painting, if there be no varnish of the gum resins over it, so as to render the colours liable to be injured by very little rubbing. The use of them or sope, is* however, in many cafes unavoidable, and in general they are the only substances employed for this purpose.
Sope is much of the fame nature with the last mentioned substances ; being indeed only oil incorporated with salts of the fame kinds, rendered more powerfully dissolvent by means of quick-lime : for which reason it is some thing more efficacious; but consequently more hazardous ; as it will the sooner get hold of the oil of the paintings. It should, therefore, not be used but on particular spots, that elude all other methods ; and there with great caution.
Spirit of wine, as it will dissolve all the gums and gum resins, except gum Arabic, is very necessary for the taking off from pictures varnishes composed of such substances : but it corrodes also the oils of the paintings; and softens them in such manner, as makes all rubbing dangerous while they are under its influence.
Oil of turpentine will, likewise, dissolve some of the gums used for varnish : but spirit of wine will in general much better answer that purpose. There are, however, some
times spots of foulness, which will give way to spirit of turpentine, that resist most other substances used in this intention : and it may, therefore, be tried where they appear to fail.
bu$ very sparingly, and with great caution jW it will very fpon act even on the dry oil of the painting.
' Essence of lemons has the fame powers as ©il of turpentine : but is, moreover, a much stronger dissolvent ; and should*, therefore, only be used in desperate eases, where spots seem indelible with regard to all other methods. Spirit of lavender and rose-mary, and Other essential oils, have the fame dissolving qualities as essence of lemons ; but they are in general dearer ; and some of them too power ful to be trusted near the colours.
Whenever paintings are varnished with gum Arabic, glair of eggs, or isinglass, the varnish should be taken off when they are to be clean ed. This may be easily distinguished by wet ting any part of the painting, which will feel clammy, if varnished with any substance dissolvable in water. In such cafes, the, taking
off the varnish will frequently alpne render the painting intirely clean : for if it have been laid on thick, and covered the surface every where, the foulness must necessarily lye upon it. The manner of taking off this kind of varnish must be done by means of hot water and a spunge ; the picture or painting being laid horizontally. The waiter may be nea? boiling hot ; and may be used copiously at first with used in Paint in <s." %z%
with the spunge : but when the varnish appears to be softened, and the painting more naked, k should be used cooler ; and, if the varnish ad here, so as not to be easily brought off by a spunge, a gentle rubbing with a linnen cloth may be used; the cloth being frequently wrung; and wet again with fresh water a little warmish.
Where paintings appear by the above trial to be varnished with the gum-resins, or fuel* substances as cannot be dissolved in water, it is proper, nevertheless, to wash them weft with water pretty warm, by means of a spunge; which will sometimes be alone sufficient to clean them, even in this case : but if there yet appear any foulness, rub the painting over with olive oil made warm, or butter ; and any parts appear smeary, or any foulness seem to mix with the oil or butter, pursue the rubbing gently; taking off the foul oil, and addingfresh till all such foulness be wholly removed.
Let the oil be then wiped off with a woollen cloth, and if the picture require further clean ing) the wood-ashes, or pearl-ashes, must be used in the following manner ; which, indeed, as to the first part is not widely different from' the method commonly used.
" Take an ounce of pearl-ashes, and dis--" solve them in a pint of water : or take two-IC pounds of wood-ashes, and add to them " three quarts of water, and stir them well
" in the water once or twice in an hour for " half a day ; and then, when the earthy part " of the ashes has subsided, pour off the clear 2 *
'* fluid, and evaporate it to a quart ; or is it " appear acrid to the taste at that time, three " pints may be left. Wash by means of " spunge the painting well with either of
*' these solutions, or lyes (which are in fact " the fame thing) made warm; and rub any " particular spots of foulness gently with a " linnen cloth till they disappear : but if they " appear to remain unchanged by the lye, do " not endeavour to take them off by meer ,l force of rubbing; for that would infallibly " damage the colours under the spots before " they could be removed : but in this cafe 11 they should be left to be tried by the spirit " of wine, or the essential oils of turpentine " and lemons. Where thick spots seem to cc give way in part, but yet resist in a great " degree to this lye, a little strong sope-suds c' may, in some cases, be used, if with great •c caution : but it should be prevented as cc much as possible, from touching any partcc of the painting, except the spot itself: and, c' as that disappears, the fope should be di-" luted with water, that it may not reach the cC oil of the colours in its full strength. If, " however, all this be done upon a strong c' coat of varnish, there will be less hazard ; " and, in such cases, the washing freely with " the wood-ash lye, or weak sope,suds, will *£ frequently do the business effectually with- " out any material damage : but it requires
" some judgment to know where paintings '' may be so freely treated ; and, with respect " to
" to those of great value, it is always best to " proceed by more circumspect methods ; " and to try the more secure means I have " above directed, before these rougher be " used."
Some use the wood ashes with the addition of water only, without separating the solution of the salts from the earth ; which, when so used, assists in scrubbing the foulness from the painting : but all such practices are to be con demned ; as the finer touches of the painting are always damaged in a greater or less degree, where any abrading force is employed in clean ing it.
Where spots appear, after the use of all the above mentioned methods, spirit of wine, or, if that fail, oil of turpentine, and in the further case of its default, essence of lemons, must be applied. The spots should be lightly moistened with them ; avoiding to suffer them to touch any more of the sursace than what is covered with the foulness ; and the part mould be immediately rubbed with a linnen cloth, but very gently ; observing at the same time to desist, if the colours appear the least affect
ed. After a little rubbing olive oil should be put on the spot, where oil of turpentine and essence of lemons are used ; and water where spirit of wine is applied ; which being
taken off by a woollen cloth, if the foulness be not wholly removed, but appears to give way, the operation must be repeated till it be intirely obliterated.
Q^\ Where paintings appear to have been varnished with those substances that will not dissolve in water, and after the careful use of the above means the foulness still continues, or where, as is very often found, the turbidness, or want of transparency or the yellow colour of the varnish, deprave the painting so as to destroy its value, such varnish must be taken off.
The doing of which, though attended with the greatest difficulty to those who proceed by the methods now in use, and which indeed is seldom done by them at all, but with the destruction of the more delicate teints and touches of the painting, is yet very easily and safely practicable by the following method.
" Place the picture or painting in an hori-" zontal situation ; and moisten, or rather " flood, by means of a spunge, the surface " with very strong rectified spirit of wine;
,c but all rubbing more than is necessary to " spread the spirit over the whole surface must " be avoided. Keep the painting thus moist-" ened, by adding fresh quantities of the spi-" rit for some minutes : then flood the whole " surface copiously with cold water ; with " which, likewise, the spirit, and such part " of the varnish as it has dissolved, may " be washed off. But in this state of it, all ' rubbing, and the flightest violence on the ' surface of the painting, would be very de-' trimental. When the painting is dry, this
c operation must be repeated at discretion, till ' the whole of the varnish be taken off."
In pictures and paintings, which have been long varnished, it will be found sometime?, that the varnish has been a composition of linseed oil, or some other substantial oil, with gums and resins. If such paintings cannot be brought to a tolerable state, by. any of the above mentioned means, which may in this cafe be freely used, the mischief may be deem ed to be without remedy. For it is absolutely impracticable to take off such a varnish, as it is more compact and indissoluble than the oil of the painting itself ; and could only be wrought upon by those menstrua and dissolvents, which would act more forcibly on the paintings: such pictures must, therefore, be left in the state they are found ; except by be ing freed from any foulness that may lye upon this varnish ; and may be cleared away by the methods we have before directed. The coat of this varnish may, indeed, be sometimes made thinner by anointing the surface of the painting with essence of lemons ; and then putting on olive oil, which, when rubbed off,
by a soft woollen cloth, will carry away the essence with such part of the varnish as it may have dissolved : but this requires great nicety ; and can never be practised without some hazard of disordering the colours of the painting.