Chemical apparatus; Electroplating; Glass blowing and working; Glass coatings; Glass grinding and polishing; Lampwork; Mirrors
Two sticks of quartz are introduced and caused to meet just in front
of the inner cone--the hottest part of the flame. They are then
drawn apart so as to form a fine neck, which softens and is bent in
the direction of motion of the flame gases. When fusion is complete
the neck separates into two parts, and a thread is drawn from each of
them. By alternately lightly touching the rods together, and drawing
them apart, quite a mass of threads may be obtained in two or three
minutes, when the process should be stopped. If too many threads get
entangled in the pins, one gives one's self the unnecessary trouble of
separating them. On taking down the card it will be found that the
threads have been caught by the pins; but the card now being laid
black side upwards, the former easily slip off the points.
Threads at least a foot long, and perhaps vastly longer, may be
obtained by this method, and are extraordinarily fine. When I first
read Professor Nichols' statement (Electric Power, 1894) as to the
value of these fibres for galvanometer purposes, I was rather
sceptical on the ground that the threads would tend to get annealed by
being drawn gradually, instead of suddenly, from a place of intense
heat to regions of lower temperature.
Now annealing threads by a Bunsen makes them rotten. The threads
being immersed in the hot flame gases could only cool at the same rate
as the gas, and it was not--and is not--clear to me that annealing
of the threads can be avoided. On the other hand, it may be possible
that a thread cooled slowly from the first does not suffer in the same
way as a cold thread would do when annealed in a Bunsen flame.
Again the velocity of the gases is beyond doubt exceedingly high, so
that the annealing, even supposing it to be deleterious, might not be
carried very far. Threads drawn by this method and measured "dry,"
i.e. by mounting them on a slide without the addition of any liquid,
turned out to have a diameter of about 1/20000 of an inch.
I do not think I could manage to mount such fine threads without very
special trouble. All the threads lying on the board, however, were
found in reality to consist of three or four separate threads, and
there is no reason why several threads should not be mounted in
parallel, provided, of course, that they are equally stretched and
touching each other. Equality of tension in the mounting could be
secured by making one attachment good, then cementing the other
attachment to the other end of the threads, and "drawing" the two
attachments slightly apart at the moment the cement commences to set.
This method may turn out to be very valuable, for, so far as I can
see, the carrying power would be increased without an increase of
torsional stiffness of anything like so high an order as would be the
case were one thread only employed. On the other hand, the law of
torsion could hardly be quite so simple, at all events, to the second
order of approximations.
Public-domain text, read in full here on John Shaqi.
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