The herald., 1894-09-16
Has a VII Or rs o,z...
Glass Peculiar and Dirirrit su5stance 81
Handle In s.s..ut,c.urs.

handle In MG..rt.c.1ra.
A writer in Tho Optical states thai
glass is substance whic.i, as tho glas.
blower says, he's u VIII Ct its os7n. Il
is very often difficult to tell how par
ticular piece is going to act rnder cer-
tain conditions, even after having &c ,ted
other pieces Of The same batch. y
When subjected to tho heat, one end Of
tube will sometimes respond different
" from tho other crG. This is in q
measure due 10 unequal chilling. occa-
stoned possibly by 4 sudden draft of air
while it is III 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 chamcleonlike, and every
process succeeds better with those who
seem to have lsaaoll wlach is generally
obtained BY long practice
The cutting of glass heads the list of
tho uncertain processes, for it has no
definite cleavage, and its separation is
modified by the surrounding tempera-
trrc. The simplest separation is On fiat
glass i'll q straight line Hero all that
is necessary is adeep and regular scratch
with GLACIERS diamond, firm and
speedy bend away from the main piece.
and the parts crack along the desired
line. These GLACIERS diamonds may be
purchased and generally prove satisfac
tory, but it is more economical to pur-
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 fled little upon the side nearest
the ruler to obtain, after trial, the best
cutting angle for the diamond. Another
instrument for cutting glass less cxpen-
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.
ocut tubes carefully scratch at right
angles to the axis deep notch, either
with the diamond, triangular file or o
glassblower' knife. Heat a piece Of
brass rod until a small globule - sars
on the end and press this NJ 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 if
it's thickness be uniform. In the case of
variable thickness uneven edges result,
and these must be filed down to avoid
sharp cutting splintors. 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 a heavy electric current By
wrapping the wire round heavy bottle
or jar and allowing the current to pass
for 10 or 10 seconds the stoutest walled
vessel may be easily separated if touched
on the heated line with cloth dipped
in water