INK
INK ( 5<
blacknefs to a certain degree, but not fo fpeedilynor fo completely.
The blacknefs of common ink is almoft in-ftantly and irrevocably deftroyed by the oxy-muriatic acid, and hence any writing may beeffaced by this method completely. To preventthis mifchief, which might often be a feriousone, feveral additions have been propofed tocommon ink, of which by far the beft is lamp-black or charcoal, in impalpable powder, on■which the acid has no effect. The lamp-blackihould be of the lead oily kind, as it does notreadily mix with the ink, and fome pains muftbe taken to incorporate them. On this accountperhaps common charcoal is preferable. Abouta quarter of the weight of the vitriol ufed willbe amply fufficient. This will not fade byage.
The well known and much admired Indian or China ink, is brought over in fmall oblongcakes, which readily become difFufed in waterby rubbing, and the blacknefs remains fufpendedin it for a confiderable time, owing to the ex-treme fublety of divifion of the fubfiance thatgives the colour, and the intimacy with whichit is united to the mucilaginous matter thatkeeps it fufpended.
Indian ink does however depofit the wholeof its colour by handing, when it is difFufed ina confiderable quantity of water. Dr. Lewison examining this fubftance found that theink confifted of a black fediment totally info-luble in water, which appeared to be of thenature of the fineft lamp-black, and of ano-ther fubftance foluble in water, and whichputrefied by keeping, and when evaporated lefta tenacious jelly exa£tly like glue or ifinglafs.It appears probable therefore that it confifts ofnothing more than tliefe two ingredients, andprobably may be imitated with perfefft accu-racy by ufing a very fine jelly, like ifinglafs orfize, and the fineft lamp-black, and incorpo-rating them thoroughly. The fineft lamp-blackknown is made from ivory fhavings, and thencecalled ivorj-blach.
Ink. Printers.
This is a very fingular compofition, partakingmuch of the nature of an oil varnifh, but differ-ing from it in the quality of adhering firmly tomoiftened paper, and in being to a confiderabledegree foluble in foap water.
It is, when ufed by the printers, of the con-fidence of rather thin jelly, fo that it mayhe fmeared over the types readily and thinly,
c Encycl. Arts and M<
3 )
when applied by leather cufhions, and it driesvery fpeedily on the paper without runningthrough to the other fide, or paffing the limitsof the letter.
The method of making printer’s ink is thusdeferibed by Dr. Lewis.
Ten or twelve gallons of nut oil are fet overthe fire in a large iron pot, and brought to boil.It is then ftirred with an iron ladle, and whilftboiling, the inflammable vapour riling from iteither takes fire of itfelf or is kindled, andfuffered to burn in this way for about half anhour, the pot being partially covered fo as toregulate the body of the flame, and confequentlythe heat communicated to the oil. It is fre-quently ftirred during this time that the wholemay be heated equally, otherwife a part wouldbe charred and the reft left imperfect. Theflame is then extinguifhed by entirely coveringthe pot. The oil by this procefs has much ofits unftuous quality deftroyed, and when coldis of the confiftence of foft turpentine, and isthen called varnifh. After this it is made intoink by mixture with the requifite quantity oflamp-black, of which about 2± ounces are fuffi-cient for 16 ounces of the prepared oil. Theoil lofes by the boiling about an eighth of itsweight, and emits very often five fumes. Seve-ral other additions are made to the oil duringthe boiling, fuch as crufts of bread, onions,and fometimes turpentine. Thefe are keptfecretby the preparers. The intention of themis more effeftually to deftroy part of the un&u-ous quality of the oil, to give it more body, toenable it to adhere better to the wetted paper,and to fpread on the types neatly and uniformly.
Befides thefe additions, others are made bythe printers, of which the moft important isgenerally underftood to be a little fine indigo inpowder, to improve the beauty of the colour.
For further obfervations on the nature offixed oils, and the alteration they undergo byheat, fee the article Oil. (Fixed.)
Red printers ink is made by adding to theVarniflo about half its weight of Vermillion. Alittle carmine alfo improves the colour. 0
Inks. Coloured.
Few of thefe are ufed except red ink. The pre-paration of thefe is very fimple, confifting eitherof decoftions of the different colouring or dyeingmaterials in water, and thickened with gum ara-bic, or of coloured metallic oxyds or infolublepowders merely difFufed in gum water. Theproportion of gum arabic to be ufed may be thefame as for black writing ink, Ail that appljo*
iers. vol. iii. p 518.
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