294 
THE YOUNG SCIENTIST. 
and "wherefore" of this process, as it 
may truly be said that more time and 
money have been wasted in this part of 
the manufacture than in any previous 
part of the process. It consists, then, in 
applying heat to the india-rubber under 
pressure, in such a degree as to expel the 
sulphureous gas which permeates it, and 
no more. This has the effect, firstly, of 
turning the color of the caoutchouc to 
Fig. 1.— PLATE. Fig. 2.— PRESS. 
that slaty tint with wbich we are all so 
familiar; secondly, of rendering it beauti- 
fully elastic and pliable; and thirdly, to 
permanently retain the impression which 
has been imparted to it. The success of 
the operation depends in a small measure 
on the skill of the operator, and nearly 
altogether on the india-rubber employed. 
It is a mistake to endeavor to procure it 
at an ordinary rubber dealer's ; they are 
ignorant of the use for which it is re- 
quired, and thus may supply the pur- 
chaser with a wrong kind ; or if they do 
happen to have it in stock, it will be very 
probably in the form of large rough 
blocks, utterly imsuited for the purpose. 
Place the whole apparatus — press, 
frame, plates, and rubber, over a clear 
fire or a gas burner, whichever be most 
convenient. A Bunsen burner, size 2, 
in practice, will be found to be the best 
in the long run, the absence of soot and 
smoke being a very important item in the 
work. In this case the apparatus must 
be placed on an iron tripod, which may 
be bought at most druggists for twenty- 
five or thirty cents. 
In either case, do not touch the press 
until the hea,t has thoroughly penetrated 
every part of it, which will take two or 
three minutes; then, taking an old piece 
of cloth between the fingers, gradually, 
carefully, and evenly screw down the 
press, at short intervals, until the four 
pins on Fig. 1 penetrate right through 
the layers of india-rubber, and at last 
rest on the upper edge of the frame. The 
press is now quite tight, and the screws 
can no longer be used; and now the 
operator can examine the rubber, a thin 
edge of which will be exposed between 
the plates. As soon— generally in about 
fifteen minutes— as the rubber turns to a 
blue color, it is a sign that the vulcaniza- 
tion is complete ; and the whole apparatus 
must now be removed from the source of 
heat, and, with the parts still together, 
left to cool ; or, if expedition is necessary, 
it may be placed in cold^ water. When it 
is quite cold, unscrew the press, take out 
the frame, with the rubber still adhering 
to the plaster in it, and carefully separate 
the rubber from the cast; they may stick 
together slightly, but it is only a chance. 
When separated, you will find that you 
have produced an absolutely faultless 
fac-simile in vulcanized caoutchouc of 
the original leaden type you used; in 
other words, you have made a Eubbek 
Stamp. 
The only thing that now remains to be 
done is the mounting of the rubber on 
the brass or wood, as the case may be, 
fixing the same in a handle, and placing 
the whole in a box, with the pad and 
ink necessary for its manipulation. 
The piece of brass is taken, and, by 
means of the square shank turned on it, 
forced into the hole in the handle; the 
rubber is then, after the edges have been 
trimmed with a pair of scissors, cemented 
on the brass with a thick solution of 
methylated spirit and gum shellac; it 
will be dry in one or two hours. 
The cheaper stamps are all fastened on 
wood, which answers nearly as well as 
brass. Glue or cement may be used for 
attaching the rubber to the wood. 
In the case of an oval or round stamp 
being required, an oval is bought of the 
size chosen, at a dealer in printer's 
materials, and being type higli, and the 
centre and edge being left blank, or 
"pierced for type," the letters are put 
into it and wedged in their places by 
little pellets of tissue paper, small leaden 
spaces, or anything handy. 
