| Scientific
glassblowing is considerably different from what one thinks
of as glassblowing. Visions of Venetian masters working with
long blowpipes, dipping into glowing furnaces of molten glass...
not. We work from preformed tubing and other shapes made of
borosilicate "Pyrex" glass, which we buy from larger manufacturers
such as Corning, Kimble, and Schott.
Our processes are best
thought of as a combination of thermal forming and welding:
we can heat larger amounts of glass to make changes in the
general shape of the glass, and heat smaller areas to fuse
tubes and components together. We use welding torches and other
larger torch configurations, with oxygen and gas or hydrogen
for fuel. "Blowing" is certainly one of the techniques, as
is sucking, spinning, slumping, etc
In designing glass
apparatus, you can save considerable time and money by taking
note of the standard
sizes of tubing available. All too often, to our taste,
anyway, the glass is specified after everything else, resulting
in requirements for glass of a size which is not standard,
or has a very tight tolerance, which means higher expense.
Typically standard tubing sizes have diameter tolerances on
the order of several percent.
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by Charles F. Ulric
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We
use glassblowing lathes to make seals, shrink or enlarge tubing,
form shapes, and tool flanges and fittings. The glassblowing
lathe is different from machine lathes in that both the headstock
and tailstock are driven synchronously, so that a tube can
be held from both ends, turned at the same speed, and heated
to soften it to work the glass without spiral deformation.
For this reason, objects that have generally cylindrical symmetry
are easier to make. We can then add other parts to the glass
by fusing on tubing and components.
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Lawrence
Berkeley Lab 1963 - Photo courtesy Tom Orr |
In
addition, glass can be cut, drilled, and milled in the manner of
traditional machining using diamond tooling....
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...as
well as CNC waterjet cutting. The 7.5" diameter discs
shown at the left have
been cut this way, and one has been firepolished in an oven,
and had the "tabs" lifted-up. Laser cutting is possible
in quartz, but problematic for borosilicate glass. |
You can read some more in an article
by the magazine Chemical Engineering News titled "An
Essential Craft"
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