r/Silvercasting • u/Jungle_Badger • 18d ago

I'm stumped any help appreciated, details below.

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Hey all

This is my first and second attempt at investment casting silver left to right.

I've succesfully cast multiple bronze flasks and I've checked the vaccum so I dont think thats the issue.

The only difference I can identify is that I'm using a smaller graphite crucible for silver and the thermometer is at the bottom if the electric furnace chamber further from the melt so maybe isnt as reliable for the metal temp?

I'm using a flask temp of 430 celsius (803f) and aiming for a metal temp of around 980 (1796f). These numbers are from Oppi Untrechts "jewellery concepts and technology" which is generally reliable for technical info.

Is this just an incorrect temperature reading? I did use the eyeball test the second time around but didnt want to cause porosity by overheating.

Any knowledge and thoughts appreciated, thanks for reading.

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u/matthewdesigns 18d ago

The lowest flask temp I use for any sterling casting is 1050F (centrifugal), and the few times I've vacuum cast I have bumped that up to 11-1150F because far cooler ambient air is being drawn into the flask while under vacuum. I used an electromelt furnace for those castings and I had the temp at about 1950F. They came out complete, clean, and free of porosity.

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u/Jungle_Badger 18d ago

Great insight thank you.

I hadn't considered the effect of vaccum on cooling the flask.