Asheville daily citizen., 1894-08-24
GLASS WORKING.
The Delicate Process Is Attended with
Much Uncertainty.

MuCh uncertainty
A writer in the Optician states that
glass is u substance which, as the glass
blower says, has q will of its own. 1t
is very often difficult to tell how par
ticular piece is going to act under ccr-
tain conditions, even after having
tested other pieces of the same "butch. ;"
When subjected to the heat one end Of
a tube will sometimes respond diff
fcrcntly from the other end. This is
in Ia measure due to unequal chilling,
occasioncd possibly by sudden
draught of air while it is in process
Of manufacture. No piece of glass is
absolutely reliable. Its working is,
therefore, at certain stages, most un-
certain, and one person may have en-
tircly different experiences from
another. 1t is chameleonlilse, 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 it's separation Is
modified by the surrounding tcmpcra-
ture. The simplest separation is on
fiat glass In straight line. Here all
that is necessary Is n deep and regular
scratch with glazicr's diamond, u
firm and speedy bend away from the
main piece, and the parts crack along
the desired line. These glazicr's dia-
monds may be purchased and general
ly prove satisfactory, but 1t is more
economical to purchase from some dia.
mond cutter small splinter, and In
sert this into piece of brass rod hav.
ing small hole drilled into one end.
The splinter should now be cemcnted
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
insvument for cutting glass less cx'
pensivc than the diamond is the glass
blowers knife, which is piece of thin
steel tempered glass hard by heating
1t cherry rcd and then plunging 1t into
ice-cold water or mercury. Tho edge
should be sharpcncd by rubbing 1t upo,
nn old, rough emery grindstonc unit
fine saw-likc notchcs appear. 1t i.
then ready for usc and should, II mucl
used, be sharpcned repeatedly.
To cut tubes, carefully scratch o.
right angles to the axis deep notch
either with the diamond, triangular
file or glass blowers knife. Heat {
piece of glass rod until a small globul,
appears on the end and press this upo,
the scratch. The glass will thus be heat
cd more ut this point than ut any other
an unequal expansion takes place, thu
scratch giving direction to tho line O
fracture, and the tube cracks evenly i
It's thickness Is uniform. In the cas-,
OF variable thickness uneven edges re
suit, and these must be filed down Il
avoid sharp, cutting splintcrs. Man,
recipes and directions have been givel
for cutting bottles Wctting an asbcs
tos string with turpentinc and setting
1t on fire produces considerable heat II
the glass Immediately underneath 1t
By quickly removing the string nn,
plunging the bottle into cool water tn
unequal strain takes place and tn
parts separate. 1t is this locating o
tho hcnt that causes the glass to cracl
as wo wish it. Tho easiest method,
the means be ut hand, is to employ
platinum wire, which should bc hcate
white hot by the passage Of heav
electric current. by wrapping tn
wire round heavy bottle or jar I'M
allowing the current to pass for ten 0
fifteen seconds the stoutest walled YES
sci may be easily separated il touchc
on the heated line with cloth dippe
II 1xyotor