ON COeAL VARNrSMES. 25^ 



given to them, and on any apparent failure, refort to thofe 

 whofe experience may enable them to detect any fallacy there 

 may be in the proceeding. 



As it is well known that folUtion of copal is the mod valu- Remarks and 

 able of thofe varnifhes which can be ufed for the finer works of^*"''^'*^' 

 art, and as it is proved that by the procefs I have defcribed, 

 thefe folutions may be eafily made by any one in almoft any 

 fituation, it only remains to mention fome cautions which are 

 necefTary to enfure fuccefs. 



Firft, That the fpirit and camphor fhould be united before 

 the copal is added. 



Secondly, That the copal fhould be grofsly powdered before 

 it is added to the fpirit, the whole (hould then be made to boil 

 as quicklj/ aspojfibk, but not violently, and that ebullition Ihould 

 be kept up regularly till the folution be compleat. 



There feems to be no difadvantage in ufing too much cam-Effeas of an 

 phor if it (hould fo happen ; but it is difadvantageous to put overdoie 

 in too little copal; becaufe a certain quantity of fpirit will of copal, 

 take up a given quantity of copal; and if more is added than 

 will be diffolved, the fuperabundant copal will abftradt more 

 camphor from the liquid, and thus render the folution more 

 tedious and difficult, and fometimes, perhaps, entirely pre- 

 vent it. 



The advantage that attends the ufe of glafs veflels is that theciafs veffels an*! 

 folution may be feen all the time it is going on ; the difadvan-^^^^*^ of metal 

 tage is that perfons who are not accuftomed to fuch purfuits, 

 may inadvertently give too much heat, and thus fubjedl them- 

 felves to ferious accidents; but by ufing veflels of metal with 

 the precautions I have given, no accident can happen ; the 

 only difadvantage is that they cannot fee what they are doing ; 

 this is of fmall confequence, as it may alv/ays be determined 

 with fufficient accuracy by the ear whether the fpirit boils> and 

 to what degree ; and as no accident can happen, without very 

 grofs neglect, from the ufe of them, they certainly fhould be 

 preferred. 



As I have written more than I at firfl: intended, I fhall con- Condufion. 

 elude with a requeft that you will ufe your difcretion in omit- 

 ting any part or rejedling the whole of what I have written, 

 if you think the publication will not anfwer any ufeful purpofe. 

 I fend with it afuiall quantity of copal dilTolyed ia alcohol, and 



another 



