varnish. 
sented itself; and too impetuous towards 
those who opposed him. His works, which 
were published separately, were “ Projet 
d’une iiouvelle Mecbaniqne,” 4to. “ Des 
nouvellcs Conjecture sur la Pesanteur.” 
“ Nouvclle MeciiKuiqae ou statique.” Be- 
sides a vast number of separate memoirs. 
VARNISH. Lac varnishes or lacquers 
consist of different resins in a state of solu- 
tion, of which the most common are raas- 
tich, sandaracii, lac, benzoin, copal, amber, 
and asphaltum. The menstrua are either- 
expressed or essential oils, as also alcohol. 
For a lac varnish of the first kind, the com- 
mon painter’s- varnish is to be united by. 
gently boiling it with some more mastich or 
colophony, and then diluted again with a 
little more oil of turpentine. The latter- 
addition promotes both the glossy appear- 
ance and drying of the vai nish. 
Of this sort is the amber varnish. To 
make this varnish, half a pound of amber 
is kept over a gentle fire in a covered iron 
pot, in the lid of which there is a small 
hole, till it is observed to become soft, and 
to be melted together into one mass. As 
soon as this is perceived, the vessel is taken 
from off the tire, and sufi'ered to cool a lit- 
tle; when a pound of good pamter’s varnish 
is added to it, and the whole suffered to 
boil up again over the fire, keeping it con- 
tinirally stirring. After this, it is again re- 
moved from the fire; and when it is be- 
come somewhat cool, a pound of oil of tur- 
pentine is to be gradually mixed with it. 
Should the varnish, when it is cool, happen 
to be yet too thick, it may be attenuated 
with more oil of turpentine. This varnish 
has always a dark-brown colour, because 
the amber is previously half-burned in this 
operation; but if it be required of a bright 
colour, amber-powder must be dissolved in 
transparent painter’s varnish, in Papin’s ma- 
chine, by a gentle fire. 
As an instance of the second sort of lac- 
varnishes with ethereal oils alone, may be 
adduced the varnish made with oil of tur- 
pentine. For making this, mastich alone is 
dissolved in oil of turpentine by a very 
gentle digesting heat, in close glass vessels. 
This is the varnish used for the modern 
transparencies employed as window blinds, 
fire-screens, and for other purposes. These 
are commonly prints, coloured on both 
sides, and afterward coated with this var- 
nish on those parts that are intended to be 
transparent. Sometimes fine thin calico, 
or Irish linen, is used for this purpose ; but 
VOL. VI. 
it requires to be primed with a solution of 
isinglass, before the colour is laid on. 
Copal may be dissolved in genuine Ohio 
turpentine, according to Mr. Sheldrake, by 
adding it in powder to the turpentine pre- 
viously melted, and stirring till the whole is 
fused. Oil of turpentine may tlien be ad- 
ded, to dilute it sufficiently. Or the copal 
in powder may be I'lit into a long necked 
matrass with twelve parts of oil of turpen- 
tine, and digested several days on a sahd- 
heat, frequently shaking it. This may be 
diluted with one fourth or one fifth of alco- 
hol. Metallic vessels, or instruments, co- 
vered with two or three coats of this, and 
dried in an oven each time, may he washed 
with boiling water, or even exposed to a 
still greater heat, without injury to the var- 
nish. 
A varnish of the consistence of thin tur- 
pentine is obtained for aerostatic machines, 
by the digestion of one part of elastic gum, 
or caoutchouc, cut into small pieces, in 
thirty-two parts of rectified oil of turpen- 
tine. Previously to its being used, how- 
ever, it mlist be passed through a linen 
cloth, in order that the undissolved parts 
may be left behind. 
The third sort of lac-varnishes consists in 
the spirit-varnish. The most solid resins 
yield the most durable varnishes ; hut a 
varnish must never he expected to be hard- 
er than the resin naturally is of which it is 
made. Hence, it is the height of absurdity 
to suppo.se, that there are any incombusti- 
ble varnishes, since there is no .such thing 
as an incombustible resin. But the most 
solid resins by themselves produce brittle 
varnishes : therefore something of a setter 
substance must always be mixed with them, 
whereby this brittleness is diminished. For 
this purpose gum elenii, turpentine, or bal- 
sam of capaiva are employed in proper 
proportions. For the solution of these bo- 
dies the strongest alcohol ought to be used, 
which may very properly indeed he distill- 
ed over alkali, but must not have stood 
upon alkali. The utmost simplicity in com- 
position with respect to the number of the 
ingredients in a formula is the result of the 
greatest skill in the art; hence, it is no 
wonder, that the greatest part of the for- 
mulas and recipes that we meet with are 
composed without any principle at all. 
In conformity to these rules, a fine co- 
lourless varnish may be obtained, by dis- 
solving eight ounces of gum sandarach and 
two ounces of Venice turpentine in thirty- 
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