Staunton spectator. [volume] (Staunton, Va.) 1849-1896, 1894-09-05
HAS A WILL OF ITS OWN.
Glass a Peculiar and Difficult Substance to
Handle In Manufacture.

Glass Peculiar and Difficult Substance to
Handle In Manufacture.
A writer in The Optical states that
glass is substance which, as the glass
blower says, has will Of its own. 1t
is very often difficult to tell how a par
ticular piece is going to act under Ger
tain conditions, even after having tested
other pieces of the same "batch.
When subjected to the heat, one end Of
a tube will sometimes respond different
ly from the other end. This is in a
measure due to unequal chilling, occa
stoned possibly by sudden draft of air
while it is i'll process of manufacture.
No piece of glass is absolutely reliable.
Its working is therefore at certain stages
most uncertain, and one person may
have entirely different experiences from
another. 1t is chameleonlike, and every
process succeeds better with those who
seem to have knack which is generally
obtained by long practice
The cutting of glass heads the list of
the uncertain processes, for 1t has no
definite cleavage, and its separation is
modified by the surrounding tempera-
ture. The simplest separation is on fiat
glass in a straight line. Here all that
is necessary is a deep and regular scratch
with a GLACIERS diamond, firm and
speedy bend away from the main piece,
and the parts crack along the desired
line. These glazier's diamonds may be
purchased and generally prove satisfac-
fo,xy bpt ~ ic moro economical fO mr.
chase from some diamond cutter small
splinter and insert this into piece of
brass rod having small hole drilled into
one end. The splinter should now be ce-
mented with marine glue and the brass
rod filed little upon the side nearest
the ruler to obtain, after trial, the best
cutting angle for the diamond. Another
instrument for cutting glass less expen-
sive than the diamond is the glassblow-
er's knife, which is piece of thin steel
tempered glass hard by heating it cherry
red, and then plunging it into ice cold
water or mercury. The edge should be
sharpened by rubbing it upon an old,
rough emery grindstone until fine saw
like notches appear. 1t is then ready
for use and should, if much used, be
sharpened repeatedly.
To cut tubes carefully scratch at right
angles to the axis q deep notch, either
with the diamond, a triangular file or q
glassblower's knife. Heat piece of
brass rod until small globule appears
on the end and press this upon the
scratch. The glass will thus be heated
more at this point than any other, an
unequal expansion takes place, the
scratch giving direction to the line OF
fracture, and the tube cracks evenly il
it's thickness be uniform. In the case OF
variable thickness uneven edges result,
and these must be filed down to avoid
sharp cutting splinters Many recipes
and directions have been given for cut
ting bottles Wetting an asbestus string
with turpentine and setting it ON fire
produces considerable heat in the glass
Immediately underneath it. By quickly
removing the string and plunging the
bottle into cool water the unequal strain
takes place and the parts separate. II
is this locating of the heat that causes
the glass to crack as we wish it. The
easiest method, if the means be at hand,
is to employ platinum wire which
should be heated white hot by the pas
sage of heavy electric current. By
wrapping the wire round a heavy bottle
or jar and allowing the current to pass
for 10 or 5 seconds the stoutest walled
vessel may be easily separated if touched
ON the heated line with cloth dipped
in water.