INDIA-RUBBER COURT-PLASTER. 
39 
cient quantity of water over a water bath, and laid on with 
"a flat hog-tool" while warm. It is requisite to use great 
caution in spreading the plaster evenly, and in one direction; 
and a sufficient number of coatings must be given to form a 
smooth surface, through which the texture of the fabric is 
not perceptible. Each coating should be perfectly dry be- 
fore the succeeding one is given, and placed in a situation 
free from dust, and where a draught of air would facilitate 
the drying. The quantity of water used, and the weight of 
the two materials, must be a little varied according to the 
season, and the gelatine strength they possess. 
Lastly, the plaster being ready to receive the polishing 
coat, which gives also the balsamic effect to it — a prepara- 
tion is made in nearly the same manner as the tinctura ben- 
zoini composita of the Pharmacopoeia, with the addition of 
more gums ; this preparation must be laid on once only, 
and with a brush kept for the purpose. For making plas- 
ters on colored silk, it is o^ltffl^essary to select the silk a 
shade deeper than the color required, as the plaster causes it 
to appear a little lighter! M 
The process being finished, the plaster must be cut out of 
the frame with scissors, as near to the canvass to which it is 
sewed as it will admit. For sale, ft is cut up in squares, 
which is best done by means of a compass and rule. 
I have tried various solvents for India-rubber, and find 
none answer so well as those above mentioned. Ether dis- 
solves it with facility, and possesses the advantage of clean- 
liness, but it is much more expensive, and evaporates so 
rapidly, that it is almost impossible to spread the solution 
smoothly on the silk ; naphtha evaporates more slowly, 
and is, therefore, preferable, but the quality requires atten- 
tion, as it may be obtained almost free from that kreasote 
smell which is the only objection to its use. The addition 
of a small quantity of spirits of turpentine facilitates the so- 
lution of some specimens of India-rubber. The white In- 
