MARKING COIOUR FOR LINEN, &C. ^07 



•If the colours of foirituous varnilhes were not fubjea 10 the- Varnifli colours 

 v- - j j • i ? T are e q ua|| y faulty 



inconvenrence of too (peedy evaporation and drying they would in this re r pe &. 



be inadmiffibleon another account, namely, that the turpentine 

 and refins are eafily converted into foap. Gum copal is equal- Copal yield* to 

 ly unfit for marking colours, becaufe it quits the piece by boilin S water * 

 fimple ebullition in water. But as the varnifli which I have 

 made defends veflehr of copper or any other metal from the 

 action of acids of a certain ftrength as well as from that of the 

 atmofphere, I' have thought it might not be unacceptable to 

 defer ibe its competition in this place. To obtain this varnifh Procefs for m^Ir- 

 from copal as pale and as clear as water, this gum mud be re- j^* ^oplMn 

 duced to very fine powder and expofed with twelve parts of powder is dif. 

 the fineft oil of turpentine for feveral days, or until it (hall be {o]v / d }? ^ at 

 completely diflblved at a moderate heat on a land bath in a j n ii of turpen- 

 capfule of brafs, (lone ware, or porcelain, taking care to ftir tine * 

 it as- often as poflible with a rod of glafs. At the moment 

 when the confidence of fyrup begins to take place, the entire 

 folution of the copal is effected by agitation, particularly if a 

 (mail quantity of oil of turpentine be added from time to time 

 to fupply the lofs by evaporation. Three fourths of the oil of 

 turpentine which is loft by evaporation when open veflels are 

 ufed, may be faved by performing theprocefs in a long necked 

 mattrafs, which is to be expofed on a fand bath a fufficient 

 time to complete the folution of the copal, and fhaking it very 

 often. The varnifh obtained by either of thefe methods be- 

 comes yel.'owifh if the heat be urged too ftrongly; and as by 

 its too glutinous confidence it would be difficult in its applica- 

 tion, it is convenient, infiead of diluting it with oil of turpen- The copal var- 



tine, to mix it with one fourth or one fifth part of its weight of J 1 '? 1 , 18 >° , be , dU 



r t> luted wan aico- 



alcohol, taking care not to ufe too much, becaufe an excefs hoi. 



would render it of a milky white by the precipitation of part 



of the copal, which cannot admit in its folution more than a 



certain quantity of alcohol without precipitating. VefTels of Metallic veffefe 



brafs or of any other metal may receive one, two, or three ^"bakS lu^' 



coatings of this varnifli, and mull be each time well dried in them may be 



the oven. After this treatment they may be wafhed with boil- ex P ofed t0 boi [- 



. J ing water with- 



ing water without injury, and may even be expofed to a ftill out injury, 

 greater heat without the varnifli coming off; but thefe veffels 

 muft not be rubbed with fand or other bud bodies. 



By means of oil of turpentine, which evaporates and dries Aa oily com- 

 lefs fpeedily than alcohol, I fucceeded in making a black com- ^J^f^t' 



pofition other goods. 



