THE YOUNG SCIENTIST. 
143 
intended for frame, but are just about the 
right size for table and compass-saws. 
The clamp shown in a previous paper 
will answer very well for holding any of 
these saws that are wide enough to be 
held, and when the blades are very narrow 
they may be filed in an iron vise or any 
other similar device. 
Casting in Plaster of Paris— III. 
BY MARK MALLETT. 
Tools Used hi Casting. — Wax Moulcllng. — 
Piece Moulding— Elastic Moidds— Cast- 
ing from Natural Objects. 
(Continued from page 119.^ 
HE tools required for casting are 
few and simple, a basin and 
spoon being the chief. Yet for 
backing up both niould and 
cast, a mason's trowel of small size will 
be found useful, and a " drag " will be re- 
quired for smoothing the backs of casts, 
grounds, etc. A drag some three inches 
long, such as that shown in Fig. 1, can be 
cut with a file from any piece of fiat steel ; 
an old steel stay-bone, for instance, makes 
capital drags. For use in mending, and 
for various purposes, a small steel spatula 
will be indispensable. This instrument 
is shown in Fig. 2. It 
costs about twenty 
cents. One end forms 
the spatula, the other 
is a notched blade 
ULJJLLAJ-RJLA-fc^ for scraping plaster. 
Fig. ].— DRAG FOR Those commonly sold 
SMOOTHING BACKS OF + +1. 
CASTS ETC. have angular teeth, 
but an improved form 
has square teeth like those of the drag. 
These give a far better surface to the plas- 
ter. For working on the plaster cast, small 
gouges of various degrees of curvature 
(Fig. 3) are sold, also " riffles," which are 
diminutive rasps ; but these things may 
well be done without by the beginner. 
Indeed, good and experienced model- 
lers, as a rule, avoid working on the 
plaster cast as much as possible, choos 
ing rather to finish their work carefully 
in the clay. A far better surface, whether 
for delicacy or effect, is to be given in the 
Litter material. It is rather the young 
modeller, who is in undue haste to cast 
his work, who will find himself obliged to 
give much time to touching-up his plas- 
ter. The tyro will see defects in the cast 
wiiich had escaped him in tlie clay. More 
especially he will be sure to find that it 
has a "lumpy" appearance— that there 
are hills and hollows where there ought 
to be flat surfaces or regular curves, and 
this he will have to remedy. Sand-paper, 
if used firmly, will do this. The right 
sizes are middle and fine No. 2 ; coarser 
will scratch the work, and finer will be- 
come choked directly. 
Fig. 2. — COMBINED SPATULA AJSID SCRAPER. 
Fig. 3. — GOUGE FOR PLASTER CASTING. 
It should be remembered that it is 
whilst fresh from the mould that the cast 
is in the best state to be worked upon. 
There are cases in which the mould may 
be worked upon with advantage. For in- 
stance, suppose the model to be a relief, 
and that in course of the work the back- 
ground on which it is formed has lost its 
original truth and evenness. The projec- 
tions of the model may render it difficult 
to get at and correct this. But in the 
mould, where everything is reversed, the 
ground becomes the most prominent and 
easily reached part, and by the use of the 
drag we can in a few minutes make our 
ground perfectly true and smooth. Again, 
we may wish to put a name or other in- 
scription on some part of our model in 
raised letters. To model raised letters in 
the clay would be a work of considerable 
time : by incising them, in reverse, in the 
mould, which will be quickly done, we 
shall secure precisely the same result, as 
the letters will appear raised in the cast. 
Some persons object to the brilliant 
whiteness of plaster, and like it better 
" toned down." It must be admitted that 
the effect of toned plaster is more ar- 
tistic. Yellow ochre imparts a pleasing 
tone. To give a uniform tint take as 
much water as there is any possibility of 
your requiring for mixing the fine plaster 
