VAR
VAR
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This valuble fubftance is employed in all thethree kinds of varnifli, to which it communi-cates an uncommon degree of hardnefs.
11. Amber.
This is alfo a very valuable ingredient, butits application is principally confined to the co-loured and opake oil varnifhes.
12. Afphaltum.
This bitumen is extensively ufed in the beltblack oil varnifhes.
This fubftar.ee is ufed only in the oil varnifhwith which balloons are covered:
I. Alcoholic varnijhes.
Alcoholic varnifhes are prepared with lefstrouble than others, they are eafily applied,they foon dry, and are entirely free from anydifagreeable odour; on this account they arein very general eftimation. They are howeverin return, very liable to crack, or fcale off, andare incapable of refilling blows or long con-tinued fridlion.
The compofition of thefe varnifhes, thoughupon the whole fufficiently fimpie, requires afew precautions which we fliall proceed tomention. In the firft place, care fhould betaken not to add more refin than the fpirit cantake up; for moft refins, however homogeneousthey may appear to be, confift of parts unequal-ly foluble in alcohol; the confequence of a fu-perfluity of refin therefore will be, that the moftfoluble parts alone will be taken up, and the re-fulting Varnifh will be found to be much fofterand lefs durable than if only fuch a quantity ofrefin was added as juft fufficed to faturate the al-cohol. Indeed the very beft way of proceedingis to add the refill by fmall portions at a time,taking care not to add a frefli quantity till thewhole of the preceding is taken up.
Secondly, a mixture of two or more refrns isfoluble in a lefs quantity of alcohol than wouldhave been required for the folution of each fe-parately. This is particularly the cafe withthofe compounds into which copal or fandarachenter; thefe fubftances, efpecialiy the former,being but very fparingly foluble by themfelvesin alcohol.
Thirdly, much depends upon the. purity ofthe alcohol. If diluted to a certain degree withwater it is incapable of adding even 011 thefofteft refins ; and for copal varnifhes the high-eft polishle degree of retdification is abfolutelyefiential. The addition of camphor Angularlyfacilitates the folution of copal and the moreintradable refins, but u ufed in too great a pro- -
portion it makes the varnifli mealy, and tfi-minifhes its tenacity.
Fourthly, during the folution of the refills itis expedient that they fhould expofe as largea furface as poifible to the adion of 'thefpirit; for it not unfrequently happens, efpeci-aliy when heat is applied, that the refills runtogether into a tough mals, after which theirfolution goes on very fiowly : this inconveniencemay be obviated by mixing the relins with ra-ther coarfely pounded glafs.
The following are fome of the moft approvedreceipts for alcoholic varnilhes.
i". Take' of clean maftieh 6 ounces; and offandarach 3 ounces, and reduce the mixture tofine powder in a clean Wedgwood mortar:to this add 4 ounces of coarfely pounded glafs,and pour the mixture into a three pint flafkcontaining a quart of highly redified alcohol :flop the flafk loofely with a cork, and let theingredients digeft together in a warm room forthree days, fliaking the mixture frequently inthe interval. Then melt three ounces of veryclear Venice turpentine, by putting it into a cupfet in hot water, and as foon as it is perfectlyliquefied pour it into the alcoholic folution,alfo previoufly warmed, and then digeft thewhoie in hot water for two hours; ftirring itup frequently with a rod of glafs, or a flick ofwhite wood. When the digeftion is finifhedlet the flafk Hand quiet for about a week in awarm room, and after that ftrain the varnifhinto a bottle through a little cotton wool.
2. Take of copal that has been liquefied, andafterwards very finely pounded, 3 ounces, ofclean maftieh 3 ounces, of gum fandarach 6ounces, and- of pounded glafs 4 ounces: mixthe ingredients with a quart of alcohol and di-geil them as already direded : then add 21-ounces of clear turpentine.
This is a ftrong and durable varnifli whichmay be applied to chairs and other articles offurniture.
3. Take of fandarach 4 ounces, of feed lae2 ounces, of maftieh 2 ounces, and of elemi1 ounce ; digeft the whole in a quart of alco-hol moderately warm, and when the folutionis compleat add 2 ounces of Venice turpen-tine. This forms a good varniih for violinsand other mufical inftruments.
4. fake of feed lac 8 ounces, and digeft itfor three or four days in a warm place whh aquart of aicoho ; when the folution is com-pleat ftrain it through flannel to feparate theimpurities, and the- clarified liquor is the co«x-mqn lac varnifh..