Procefs to diffelue Copal in Alcobol. 6s 
Vikewifé important that the fpirit of turpentine fhould be of 
the beft quality. T have never fucceeded with that w hich is 
fold at the colour-fhops; but whenever I procured my fpirits 
at Apothecaries’ Hall, I have diffolved the copal, by the pro= 
cefs I have decribed, without difficulty. 
This varhifh is of a rich deep colour when viewed in thé 
ag but feems to five fo Coléue to the pictures i it is laid 
on: if left iri the damp, it remains facky, as it is called, a 
tad time; but ifkept in a warm room, or placed in the 
fun, it diies as well as any other turpentine varnith; and 
when dry, it appears to be as durable as any other folution 
of copal. 
To diffelve Copal in Alcohol: 
Diffolve half an ounce of catnphire in a pint of alcohol 
aye it in a circulating glafs, and add four ounces of copal ir 
mall pieces; fet it in a fand-heat, fo regulated that the bub- 
bles may be counted as they rife oe the bottom; and con- 
tinue the fame heat till the folution is completed. 
Camphire aéts miore powerfully upon copal that any fub- 
ftance that I have tried. If copal is finely powdered, and 4 
{mall quantity of dry camphire rubbed with it in the mortar, 
the whole becomes in a few minutes a tough coherent mafs. 
The procefs above defcribed will diffolve more copal thah the 
menftruum will retain when cold. The moft economical 
method will therefore be to fet the veffel which cofitains the 
folution by for a few days; and when it is perfectly fettled 
pour off thé clear vatnifh, and leave the refiduum for a fu- 
‘ture operation. 
This is the brighteft folution of Gopal that I have feen: it 
ig an excéllent varnitth for pictures 3, and may perhaps be found 
to be an improvement in fine Japan works; as the {toves 
ufed in drying thofe articles may drive off the camphire en- 
firely, arid leave the copal pure and colourlefs on the work: 
N.B. Copal will diffolve in fpirit of turpentine, by the 
addition of camphire; with the fame facility, but not in the 
fame quantity, as in alcohol. 
At the time I determined to lay the preceding papers 
before the Society, I conceived that the quick and cer ain 
SV OL, Y. K manner 
