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Old 26th Oct 2020, 9:21 pm   #24
MotorBikeLes
Nonode
 
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 2,346
Default Re: Small Insulated Tubes - Any Good Source?

Not a pottery "enthusiast", but once a ceramic technologist, so maybe I can add a bit.
You can not easily make a clay based ceramic ON a glass tube, plaster former or whatever, as it will simply crack as it shrinks on drying.
You could of course make a two part plaster of Paris mould, and cast your tubes (just like high class bone china cups).
However, if you have any machinery, you could make a "stupid" pug, or extrusion machine. A proper "pug" has an auger like a hand mincer, with a reduced orifice but which has a central plug, so tubes can be continuously extruded.
The so called "Stupid" is where you have a cylinder with a screw piston pushing the clay out through the nozzle. I can only do small batches, then needs retracting, opening, refilling and repeating.
Portland cement? Yes. Better still, "Ciment Fondue", or whatever is the current trade name. That is an aluminous cement, not a siliceous cement like Portland. It will withstand VERY high temperatures.
Glass tubing? We used to get Pyrex glass tubing in various sizes. We used thick wall, 3/4" for rollers on various of our glaze spraying machines. Joe Muggins used to be the one who cut (broke) it to length for the fitters to use.
Les.
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