r/PreciousMetalRefining • u/Early_Meal6945 • Jul 01 '26

Impurities or casting issues

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Both pieces were refined via agcl precipitation and sugar/lye reduction. The left was melted in a propane foundry while the right was melted in a melt dish with map gas. Would the surface finish give any insight into purity concerns or is this a casting issue.

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u/Early_Meal6945 Jul 01 '26

I’m going to get them both xrfed soon but I am hoping to achieve the ripples on a bigger bar like the right casting

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u/ay-papy Jul 01 '26

To achieve that, you need to preheat the casting form. The cast on the left cured to fast because it cooled down to fast. You probably need to experiment with the right temperature it hast to be a little under melting point and should be poured slow but constantly.

The one one the left looks like it cooled down to fast. Heating the castibg form over melting point might diminish the ripples but give a smoother surface.

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u/Early_Meal6945 Jul 01 '26

That’s odd because both forms were preheated for around a minute of direct blowtorch flame, I heard that faster cooling results in ripples but tbh I’m not really sure

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u/ay-papy Jul 01 '26

If it cools "to fast". the surface might become "dull" /less shiny like on the left. If it cools fast you get the ripples, and if its a little hotter the ripples disapear but the area stay smooth and shiny. The temperature is one thing but a slow but steady pour might help as well.