COMPOSITION OF DURABLE INK. 147 



commended from thofe in common ufe, confiib in the addi- 

 tion of pigments producing an unchangeable colour upon 

 paper. 



Ink of a permanent colour may be eafily obtained, by fuf- Ancient method 

 ... . . J _ ., , , . , ofcompofirhj 



pending various pigments in an aqueous fluid, by the interven- ] n j c> 



tion of gum, without the affiftance of the common ingredients; 

 but fuch compofitions are liable to one of the greatefi inconve- 

 niences, for the whole of the writing may be detached from the 

 paper by wafhing the manufcript with water. Such ink, how- 

 ever, was frequently ufed by the ancients. 



As a permanent colour is certainly a valuable requifite, it Speculation for 

 appears very promifing in fpeculation for the improvement of m lntofti\\i 

 this indiljpenfible article, according to the limpleft, and per- kind of ink. 

 haps the moft ancient method of com pofi tion, to fubftitute, in 

 place of the common mucilaginous fluid, as a compound vehicle 

 for the diftribution and protection of the colouring matter, the 

 folution of foine gum, or refinous fubftance, which can be dif- 

 folved in only a few liquids. After the diffipation of the thin- 

 ner part of an atramentous compound properly formed with 

 fuch a folution> the colouring fubflance will be left on the pa- 

 per, combined with a fufficient quantity of tenacious matter to 

 protect it from being injured by friction, or from being dis- 

 charged by the application of any fluid to which the writing 

 may be expofed, without injuring the paper. 



Many of the more volatile kinds of oils may be ufed in writ- Ink with oil ami 

 ing, if reduced to a proper confidence by the addition of gum refi:l • 

 or refin. Tolerable ink may be made by diflblving .30 grains 

 of common refin in 90 grains of oil of turpentine, and temper- 

 ing the folution with 17| grains of lamp black, and 2| of in- 

 digo. In a dry ftate, this composition refifts the action oflnconven 



nencc 



water, but not of fpirit. Such, indeed, will be the cafe with t0 "5* ever ^, 



. . . , compofition will 



every compofition in which the colour is merely fufpended in be fubjedl where 

 the fluid, and attached to the paper, by a fubftance of eafy fo-'! 16 c . 0,0 " r l s T £ ~ 



-,,.,- , .. . - , . , , . , , , , chanically fuf- 



iubility ; the application of the article which produced the flu-pended. 



idity of the ink, will again penetrate and foften the dry com- 

 pound. Thofe compofitions which contain a tenacious matter, 

 foluble in a few articles only, and at an high temperature, will 

 be the leaft exceptionable. 



A more infoluble kind of matter than refin fhould be ufed. Copal is m uch 

 Copal will diffolve in only a i'ew liquids,- it appears well fu P erior to refm 

 adapted to the purpofe of retaining a permanent colour upon fonofthe^ 



L 2 (he ment 5 



