• which each fort of varnish may be taken off, without any injury to the painting: for in fact, without this, there is no way of cleaning pictures in fome circumftances; but by scouring, till as well the furface of the picture as the foulnefs, be cleared quite away. I fhall therefore first give fome account of the nature of the fubftances which are, or may be used for ⚫ cleaning paintings in oil, as it regards this application of them; and then fhew, how they may be ufed, as well for the taking off the varnish, as the removing any foulness, that may lie either upon or under it.

The first, and moft general substance used for cleaning pictures, is, Water. This will remove many kinds of glutinous bodies, and foulness arifing from them; fuch as fugar, honey, glue, and many others; and alfo take off any varnish of gum Arabic, glair of eggs, and ifinglafs; and is therefore the greatest inftrument in this work. It may be used without any caution with regard to the colours; as it will not, in the leaft, 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 thofe fpots or faulness which refift even foap; as they will dif folve or corrode pitch, refin, and other bodies of a like kind, that otherwife require fpirit of wine, and oil of turpentine, which endanger the painting: and they may be used very freely, not having the leaft effect on the oil of the painting.

• Wood-ashes, or what will better answer the purpose, when ⚫ used in a proper proportion, pearl-afhes, being melted in water, make a proper diffolvent for moft kinds of matter which foul paintings: but they must be used with great difcretion, as they will touch or corrode the oil of the painting, if there be no varnish of the gum refins over it, fo as to render the colours liable to be injured by very little rubbing. The use of them, or foap, is, however, in many cafes, unavoidable, and in general they are the only fubftances employed for this ⚫ purpose.

Soap is much of the fame nature with the last mentioned fubftances; being indeed only oil incorporated with falts of the fame kinds, rendered more powerfully diffolvent by means of quick-lime; for which reafon it is fomething more efficacious; but confequently more hazardous; as it will the fooner get hold of the oil of the paintings. It fhould, therefore, not be used but on particular spots, that elude all other methods; and there with great caution.

Spirit of Wine, as it will diffolve all the gums and gum refins, except gum Arabic, is yery neceflary for the taking off

• from

'from pictures varnishes composed of such substances: but it ⚫ corrodes also the oils of the paintings, and foftens them in fuch manner, as makes all rubbing dangerous while they are under its influence.

Oil of Turpentine will likewife diffolve fome of the gums ufed for vanifh: but fpirit of wine will, in general, much better answer that purpose. There are, however, fometimes fpots of foulnefs which will give way to fpirit of turpentine, that refift most other fubftances ufed in this intention: and it may therefore be tried where they appear to fail, but very fparingly, and with great caution; as it will very foon act eyen on the dry oil of the painting.

• Effence of Lemons has the fame powers as oil of turpentine; but is, moreover, a much stronger diffolvent; and should therefore only be used in desperate cafes, where spots feem indeliable with regard to all other methods. Spirit of Lavender and Rosemary, and other Effential Oils, have the fame diffolving qualities as effence of lemons; but they are in general dearer; and fome of them too powerful to be trufted near the • colours.

Whenever paintings are varnished with Gum Arabic, glair of Eggs, or Ifinglafs, the varnish should be taken off when they are to be cleaned. This may be easily distinguished by <wetting any part of the painting, which will feel clammy, if In fuch • varnished with any fubftance diffolvable in water.

cafes, the taking off the varnish will frequently alone render the painting entirely clean: for if it have been laid on thick, ⚫ and covered the furface every where, the foulness must neceffarily lye upon it. The manner of taking off this kind of varnifh, must be done by means of hot water and a spunge; the picture or painting being laid horizontally. The water may be near boiling hot; and may be used copiously at first with the fpunge: but when the varnish appears to be foftened, and the painting more naked, it should be ufed cooler; and if the varnish adhere fo as not to be eafily brought off by a fpunge, a gentle rubbing with a linen cloth may be used; the cloth being frequently wrung, and wet again with fresh water a little warmifh.

Where paintings appear by the above trial to be varnished with the gum-refins, or fuch fubftances as cannot be diffolved in water, it is proper, nevertheless, to wash them well with water pretty warm, by means of a fpunge; which will fometimes be alone fufficient to clean them, even in this cafe: but if there yet appear any foulness, rub the painting over with olive oil made warm, or butter; and if any parts appear smea

• ry,

ry, or any foulness feem to mix with the oil or butter, pursue the rubbing gently; taking off the foul oil, and adding fresh, till all fuch foulnefs be wholly removed. Let the oil be then wiped off with a woollen cloth; and if the picture require further cleaning, the wood-afhes, or pearl-afhes, must be used in the following manner; which, indeed, as to the first part, is not widely different from the method commonly ufed.

"Take an ounce of Pearl-afhes, and diffolve them in a pint "of water or take two pounds of Wocd-afhes, and add to "them three quarts of water, and ftir 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 fubfided, pour off the clear fluid, "and evaporate it to a quart; or if it appear acrid to the tafte "at that time, three pints may be left. Wath by means of "fpunge the painting well with either of thefe folutions, or

66

lyes (which are in fact the fame thing) made warm; and rub "any particular spots of foulness gently with a linen cloth, till "they difappear: but if they appear to remain unchanged by "the lye, do not endeavour to take them off by mere force of rubbing; for that would infallibly damage the colours under "the fpots before they could be removed: but, in this cafe, "they should be left to be tried by the Spirit of Wine, or the "effential Oils of Turpentine and Lemons. Where thick spots. "feem to give way in part, but yet refift in a great degree to this "lye, a little ftrong Soap-fuds may, in fome cafes, be used, if "with great caution: but it should be prevented as much as "poffible from touching any part of the painting, except the "fpot itself: and, as that difappears, the Soap fhould be diluted "with water, that it may not reach the oil of the colours in its "full ftrength. If, however, all this be done upon a strong "coat of varnish, there will be lefs hazard; and, in fuch cafes, "the washing freely with the wood-afh lye, or weak soap-suds, " will frequently do the bufinefs effectually, without any mate"rial damage: but it requires fome judgment to know where "paintings may be fo freely treated; and, with respect to those "of great value, it is always beft to proceed by more circum"fpect methods; and to try the more fecure means I have a"bove directed, before these rougher be used."

Some ufe the wood-afhes with the addition of water only, without feparating the folution of the falts from the earth; which, when fo ufed, affifts in fcrubbing the foulnefs from the painting: but all fuch practices are to be condemned; as the finer touches of the painting are always damaged in a greater or lefs degree, where any abrading force is employed ⚫ in cleaning it.

• Where

• Where spots appear after the ufe of all the above-mentioned methods, Spirit of Wine, or, if that fail, Oil of Turpentine, and in the further cafe of its default, Effence of Lemons must be applied. The spots fhould be lightly moistened < with them; avoiding to fuffer them to touch any more of the furface than what is covered with the foulness; and the part 'fhould be immediately rubbed with a linen cloth, but very gently; obferving at the fame time to defift, if the colours · appear the leaft affected. After a little rubbing, Olive Oil 'fhould be put on the spot, where Oil of Turpentine and Effence of Lemons are ufed; and Water where Spirit of Wine is applied; which being taken off by a woollen cloth, if the foulnefs be not wholly removed, but appears to give way, the • operation must be repeated till it be intirely obliterated.

<

• Where Paintings appear to have been varnished with those substances that will not diffolve in water, and after the careful ufe of the above means the foulness ftiil continues, or where, as is very often found, the turbidnefs, or want of transparency, or the yellow colour of the varnish, deprave the Painting, 'fo as to destroy its value, fuch 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 feldom done by them at all, but with the destruction of the more delicate teints and touches of the Painting, is yet very eafily and fafely practicable by the following method.

"Place the Picture or Painting in an horizontal fituation; " and moiften, or rather flood, by means of a fpunge, the fur"face with very strong rectified Spirit of Wine; but all rub"bing more than is neceffary to spread the Spirit over the whole furface must be avoided. Keep the Painting thus moiftned, by adding fresh quantities of the Spirit for fome minutes: "then flood the whole furface copioufly with cold water; with "which likewife the Spirit, and fuch part of the Varnish as it "has diffolved, may be washed off. But in this ftate of it, all "rubbing, and the flighteft violence on the furface of the Paint

ing, would be very detrimental. When the Painting is dry, "this operation must be repeated at difcretion, till the whole of "the Varnish be taken off."

In Pictures and Paintings which have been long varnished, "it will be found fometimes, that the Varnish has been a compofition of Linfeed Oil, or fome other fubftantial Oil, with Gums and Refins. If fuch Paintings cannot be brought to a tolerable ftate, by any of the above mentioned means, which may in this cafe be freely used, the mifchief may be deemed to be without remedy. For it is abfolutely impracticable to • take

6

take off fuch a Varnish, as it is more compact and indiffoluble than the Oil of the Painting itself; and could only be wrought upon by thofe Menftrua and Diffolvents which would act more forcibly on the Paintings: fuch Pictures muft, therefore, be left in the ftate they are found; except by being freed from any foulness that may lie upon this Varnifh; 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 furface of the Painting with Effence of Lemons; and then putting on Olive Oil, which, when rubbed off, by a foft woollen cloth, will carry away the Effence with fuch part of the Varnish as it may have diffolved: But this requires great nicety; and can never be practifed without fome • hazard of difordering the Colours of the Painting.'

The above particulars will, we apprehend, be fufficient to give the Reader a competent idea of this performance, and probably induce him to perufe the whole, where he will meet with a great variety of curious and useful particulars. But he muft not expect, in a work of fuch variety, to meet with no faults, or that the Author could be practically acquainted with every thing he treats of. Thus, for inftance, he seems to be mistaken concerning the Colours generally used in Washing Maps; for he directs Red Ink for Red; Litmus, for Blue; Sap-green, and Verdigrife in Vinegar, for Green. But the Red generally ufed, efpecially for the beft Maps, is very different from what is commonly called Red Ink, being a Tincture from the flips of Scarlet Cloth: the Blue, is a Solution of Verdigrife in Water, by the affiftance of Tartar; and the Green, a Compofition of the fame Blue and the French Berry Wash.

N. B. A fecond volume of this work is just published; and we shall give an account of it as foon as opportunity will permit. B.

A Voyage to South America: Defcribing at large the Spanish Cities, InterTowns, Provinces, &c. on that extenfive Continent. Sperfed throughout with Reflections on the Genius, Cuftoms, Manners, and Trade of the Inhabitants; together with the Natural Hiflory of the Country. And an Account of their Gold and Silver Mines. Undertaken by Command of his Majesty the King of Spain. By Don George Juan, and Don Antonio De Ulloa, both Captains of the Spanish Navy, Members of the Royal Societies of London and Berlin, and Correfpond

ing