358 
THE YOUNG SCIENTIST. 
ing used together, aud spirit and oil of 
tar. 
(a.) Turpentine.— Ordinsir J spirit of tur- 
pentine is, I thinlc, too well known to re- 
quire description. It is procurable at any 
oil store at about 25 cents a gill in small 
quantities, and is what house painters use 
in mixing their oil colors. This kind is 
not, however, always to be recommended 
for painting purposes, as frequently it 
contains impurities, and has more or less 
of a tone or tint about it. The right kind 
for painting is the rectified spirit to be 
procured at an artist's material shop, 
where the price will probably be ten 
cents for a little bottle holding about two 
ounces. This spirit is as clear as the pro- 
verbial crystal, and as limpid as the 
purest water, and when fresh, is colorless 
and does not present the slightest trace 
of oil or water. This kind, and this only, 
should be used in painting. At the same 
time the common turpentine, when quite 
clear, and clean, and white, answers very 
-well, as has been noticed in Sec. 28, for 
washing the brushes and palette with, 
and for removing jiaint from the palette 
knife, etc. The oil of turpentine is also 
known as fat oil. It is viscid, much of 
the consistency of golden syrup, and has 
something of the color of clouded amber. 
This may be imrchased for 25 cents a 
small bottle, but it may also be prepared 
from turpentine by the amateur, thus : — 
Into a saucer— the flatter the better— pour 
a little spirit of turpentine, say from a 
dessert to a small tablespoonful, accord- 
ing to the size and flatness of the saucer, 
and over the saucer place a layer of mus- 
lin, sufficiently close in texture to prevent 
dust getting to the turpentine, and 3^et 
not so close as to prevent evaporation. A 
very good plan is to place the saucer, 
mouth down, on the muslin, and cut the 
latter with a l-inch margin, then make a 
narrow hem in tlie muslin, into which 
may be run a piece of round elastic, this 
should then be drawn sufficiently tight to 
catch well over the edge of the saucer. 
The arrangement is shown in Fig. 21. 
The saucer with its turpentine should 
then be put in a place where evaporation 
will be free. It should not, however, be 
put over the fire or a stove so as to hasten 
the evaporation, or the heat might dissi- 
pate the whole. When the spirituous 
part of the liquid has passed off there will 
be found left the oil at the bottom of the 
saucer. Fresh spirit may be added, and 
the process repeated until there is enough 
oil to pour off. 
(&.) Tar.— The spirit of tar is in two 
shades— one a rich amber, the other a 
dark brown, but both are alike in nature. 
The oil of tar corresponds to it in the 
same way as the oil of turpentine does to 
riG. 2-. — SAUCER FOR PREPARING OIL OP 
TURPENTINE. 
the spirit of turpentine. The spirit and 
oil of tar are of similar use to the other 
spirit and oil, and are employed princi- 
pally by those who object to the vapor of 
the turpentine as causing headache or af- 
fecting the throat. 
The spirits of turpentine and of tar are 
extremely volatile, the former being 
somewhat more so than the latter; and 
during the working, sufficient may pass 
off to render the paint somewhat difficult 
to deal with. This difficulty is, however, 
only a slight one, and is easily overcome 
by the use of a little 
(c.) Oil of Lavender, or oil of spike, as 
it is sometimes called. This is a perfectly 
volatile and fluid oil, but very much less 
volatile than either of the above-men- 
tioned spirits, and a small quantity is 
added to the other mediums used when it 
is desired to keep the work open, that is— 
to counteract its drying or fattening 
through loss of spirit. 
Caution.— Fa,t oil is not entirely free 
from one of the objections raised above, 
to the use of the mediums regarded as 
unsatisfactory, inasmuch as it too will 
boil up, or blister, or blib, or spit, if used 
in excess ; but in this case the remedy is 
easy : 1, not to use too much ; 2, if much 
must be used, it can, while fresh, be easily 
evaporated to dryness with the exhibition 
of moderate heat. 
Boiling Up.— It may here be explained 
