That old timer told me to preheat my molds for an extra 10 minutes

I always thought it was a waste of gas, but after ruining 3 castings in a row with cold shuts, I finally tried it. He said "those molds need to breathe before they take the metal" and I just shrugged it off. First pour after that extra preheat came out CLEAN, no cold shuts at all. Has anyone else had a simple tip like that make a huge difference?

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juliahall4mo ago

Yeah, that "breathe" thing sounded like nonsense to me too. I figured hot is hot, what's another five or ten minutes gonna do? But after a few bad pours I got desperate and tried it. Night and day difference, like @angela_allen53 said, it's cheap insurance. I think the issue is the moisture and trapped air that needs time to fully escape. Now I just set a timer and walk away, no more cold shuts. Hard to argue with results when you see it yourself.

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angela_allen534mo ago

Preheat time is cheap insurance compared to scrapped metal. Learned that lesson the hard way myself.

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