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Mold doesn’t fill properly

I am having troubles getting a nice, sound ingot because I can’t seem to get the mold to fill properly. My success is inconsistent. I have tried heating the mold a good deal past the point where the oil smokes and heat the metal significantly past it’s melting temperature. This works sometimes but not always. It often fills like this:

That is what you get in that size mold channel with that amount of melted metal that you are using. Try casting in a smaller mold channel to include the sprue metal in the casting. Try casting without heating the mold. Try pouring the melt into a mold that is tipped to the side just a bit to allow the air to get out easier. Coat the mold with a flame that is gas only and no O2. This will help the casting form and release. Good luck…Rob

“pouring” temperature is higher than “melting” temperature. What metal (alloy) are you trying to pour? What is it’s casting/pouring temp? From the picture, it looks like the “incoming” metal froze, the rounded end. Also why are you using oil, a VERY potential/likely
source of smoke/gassing off when the hot metal hits it. I recommend “carbonizing” the surfaces. I use a Acetylene” only gas flame and smoke any surfaces that the is or could come in contact with. There are also products you can get that are mold releases….

Good luck.


The metal is Tin bronze, 90% copper and 10% tin. It’s solidus is 954 and it’s liquidus is 1076. I heated it for 20 seconds after it fully melted. Thanks for the advice. I think ill try tipping mold to the side next time as I don’t have an acetylene torch.

I recently had this problem - never encountered it before. I came to the conclusion I was just pouring far too fast and this perhaps created an air ‘bubble’ so the rest of the hot metal would not go into the mold. I tipped the mold slightly and poured the metal more in the ‘funnel’ area and have not had a problem since. Hope this helps but who knows what goes on in the workshop sometimes.

Oil the mold before with a cloth and make the mold handwarm only. If needed tipp it a bit. Never quench it.

I think you need to make some venting channels.