Hi, When I first started in the dental industry and finished the
basics of model preparation, I was assigned to the gold department.
One of the first things that I was taught was how to glaze a
crucible. We didn’t use the clay crucibles. We used the quartz
crucibles. Quartz will melt at high enough temps so we would take
the crucible and blow out the dust. We would put 1 crank on the
broken arm casting machine and set the pin to hold it in place. The
cradle on the casting machine has 2 rails to hold the crucible
allowing the heat to primarily stay in the crucible and not be
conducted away. I would then put on the dark ‘casting goggles’ and
start gently heating the crucible being extra sure to heat the
throat where the molten metal will be conducted into the casting
flask. I would increase the heat until the entire ‘melt area’ of
the crucible was glowing white hot. The quartz has now fused into
glass and is as smooth as a newborns a**. When it cools down
sufficiently(not glowing), I would then sprinkle in some borax
making sure to get enough in the throat of the crucible. I would
then re-heat to a very bright cheery red. When the crucible cools
to the touch, you can use a black permanent felt tip to mark the
underside with the metal type you will melt in it. The wide black
sharpie will last for a long time and when it needs it, just
re-label it.
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