S E C T I O N IV.
Of .the colours proper to he ufed in varnijh painting; and the manner, of mixing and compounding them with the proper vehicles.
IN painting in varniSh, all pigments or folidcolours whatever may be ufed: and the peculiar disadvantages, which attend Several kinds, with reipeft to oil, or water, ceafe with regard to this fort of vehicle: as they are fecured by it, when properly managed, from the lead hazard of changing or flying; and will all work well, provided they be pre- viously reduced to the date of an impalpable powder.
The preparation of colours for this ufe, confids, therefore, in bringing them to a due date of finenefs: this may be bed done b^ grinding on the done, fuen as are of cohering texture, as lake, Pruffian blue, indico, verdi* grife, and didilled verdigrife, in Spirit of wine, or oil of turpentine; which lad 1 think the better of the two for this uie: but all the okers, or other earthy fubdances, together with vermilion, red lead, and turpeth mineral, require only to be previously well waSH ed over; and carmine, ultramarine, an King’s yellow, are neceffarily in a due ifa i wh wherl well prepared in their original manufacture.
The belt compofition of varnifh for fpread- ing and penciling the colours, with reaped to die convenience of working, and the binding and preferving of them, is fhcil-lac with fpirit of wine j which, when judicioufly managed, gives fuch a firmnefs and hardnefs to the work, that if it be afterwards further leaned with a moderately thick coat of fecd-lac ?arnifh, it will be almoft as hard and durable as glafs j and will bear any rubbing, or wear, nr even fcratching with a lharp pointed inftru- ment, almoft as well as enamel. The manner of preparing the Ihell-lac varnilh is as fol- ows.
“ Take of the beft Ihell-lac five ounces. s Break it into a very grofs powder : and put c it into a bottle, that will hold about three = pints or two quarts. Add to it one quart : of rectified fpirit of wine: and place the : bottle in a gentle heat; where it muft con- r tinue two or three days; but fiiould be fre- e quently well lhaken. The gum will then : be diflolved: and the folution fiiould be c filtered through a flannel bag: and, when 1 what will pafs through freely is ccme off, c. it fhould be put into a proper fized bottle; * and kept carefully flopped up fcr ufe : and “ the bag may then be prefled with the hand ** till the remainder of the fluid be forced out} M which if it be tolerably clear, may be em- “ ployed for coarfer purpofes, or kept to be N “ added to the next quantity that fhall be “ made.”
The fhell-lac varnifh being thus prepared, a proper quantity of it muft be put into fmall phials of a long form} or into fmall tin vefiels nearly of the form of glafs-phials j but in luch proportion, that they may never be filled above two thirds; and the colours muft be added very gradually, and well fhaken with the varnifh as each quantity is put in, till the proportion appear fit for working; which muft be known by trying with a pencil: and, if the varnifh appear too thick, the fault muft be remedied by the adding a little redtified fpirit of wine} which will at any time immediately dilute the mixture to any degree. The phials, or tin veflels, in which the colours mixt with the varnifh are kept, muft be always fecurely ftopt to prevent the exhalation of the fpirit; and they may be preferved in a working ftate in that manner for almoft any length of time: but they muft be always well fhaken before - they be ufed; as well as during the time of5 ufing at proper intervals j otherwife the colour will be apt to fettle to the bottom.
This is by much the beft method hithertod found out of painting in varnifh: the fhell— lac not only rendering the fpirit of wine capable of fufpending the colours much betteK- than any other compofition of this nature: but giving them tenacity and hardnefs, tha_f would render paintings on copper almoft eter-"3 nal, if not injured by fire or feme extraordinary violence: and it were to be wifhed, that in very elaborate works, this method had been always perfued inftead of painting in oil; which is fubjedl to fo many accidents from flight external violences, befides the decay and injurious change which the oil and colours fuffer from their own internal nature, and the improper means of cleaning, that few pictures or paintings of older date are to be found per- fett.
There are, however, other compofitions of varnifli, which are ufed for painting: as the feed-lac varnilh; and alfo the following j which requires, however, previoufly, the preparation of the maftic varnifli j that muft be thus mafle.,
“ Take five ounces of maftic in powder : “ and put it into a proper bottle with a pound " of fpirit of turpentine. Set them to boil “ in balneo mariae, till the maftic be diflolv- ** ed j and if there appear to be any foulnefs, “ ftrain off the iblution through flannel.”
. The maftic varnifli being thus prepared, it may be converted into a proper varnifli for painting by the following method.
** Take then gum animi one ounce. Grind ** it on the ftone with water, till it become “ an impalpable powder. Then dry it ** thoroughly: and grind it again with half
an ounce of turpentine; and afterwards ft with the colours j moiftening it with the “ maftic varnifli till the mixture be of a due “ confiftence for working with the pencil • ** when it muft be put into phials or tin ve£ “ fels, as was before directed for the compo- “ fition with fhell-lac; and diluted, where “ there may be occafion, with fpirit of tur- *c pentine.”
This is inferior in all refpeCts to the fhell- lac compofition, except where touches of pure white, or very bright colours, are wanted: which fuffer by the brown nefs of the (hell- lac ; and are preferved in this, that is nearly colourlefs: on which account, in the painting of flowers, or draperies, in miniature, the fine colours may be ufed with advantage this way, to heighten the lights j and the reft may be painted with the (hell-lac varnifli.
The method of painting in varnifh being, however, more tedious than in oil, or water, it is now very ufual in the Japan work, for the fake of difpatch, to lay the colours on with oil, diluted with oil of turpentine: taking care to have the mixture very thin; and to make the work rife from the furface as little as poflible j and when the whole is perfectly dry, to lay over it feveral coats of thick feed-lac varnifh j which will fecure the colours extremely well, though not (o as to render the whole equally hard and ftrong with the work done in fhell-lac varnifh.
The method of painting varnifhed work with oil may be greatly improved, by difiblv- ing the white gums or refin in the oils, as was before adviled p. 148, for common oil painting, in cafe of more delicate and valuable
undertakings.
undertakings. Which compofition being diluted with oil of turpentine, would work squally well with, dry much harder, and af- amilate more with the texture of the vamilh aid over or under the paintings, than the oils Imply ufed: and it would likewife be attend- :d with another advantage, which is, that the jvork would be fooner dry, and fit to receive he upper coats of varnifh; which, in large nanufadtures, is an objedt of confequence.
The manner of preparing the feed-lac var- iilh, and ufing it, being the lame for this as ©r other purpofes, will be Ihewn in its pro- jer place.