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Crucible composition and performance


All -

SUBJECT : Alleged fused silica / ceramic crucibles the ones most
frequently used in metal hand held devices for torch melting.

QUESTION: can breakdown of the crucible material occur which will
cause gassing in gold alloys similar to gassing that occurs during
investment casting of white gold alloys after heating and cooling
cycles from use events ?

EXPLAINED : The first time I use the Eurotool dish type fused silica
crucible I get great results casting fresh 14k white gold alloy, no
scrap no buttons. The second time I use the crucible I get slight
porosity 3rd time more, with increases in problems each time the
crucible is used. Materials/Equipment- stainless steel flask,
computer controlled kiln R&R white gold investment, propane as fuel,
vacuum casting table, backup secondary pyrometer to confirm flask
temp. fresh gold and alloys from industry respected refiner

QUESTION: does the metal float on flux or is it in contact with the
crucible material ? Yesterday I had a conversation with the alloy
manufacturer/ refiner who said he is having a difficult time getting
the preferred crucibles they used to use because the industry has
shut down production facilities which used to produce crucibles.

INTENDED GOAL: What goes into quality fused silica ceramic,
determine who is manufacturing crucibles, where crucibles are
manufactured, where the raw materials come from, and determine if
the crucibles are part of the problem of porosity in white gold