Hot take: Most guys are running their sand too hot for core work

I was over at a buddy's shop in Akron last week watching him pull a core out of the box and it was practically smoking. He let it sit for maybe 30 seconds before he started blowing it off and I could see the resin burning right there. I told him to let it cool down to at least 120 before he even touches it with the air hose. He looked at me like I had three heads but I showed him the difference on a test piece I ran that morning. His core had this brittle crust on the outside and mine came out clean with no dust sticking. The thing is we all want to move fast and get the next pour going but rushing the sand cooling just makes weak spots that show up when you least expect it. Has anyone else noticed that cooling time matters way more than we give it credit for?

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charlesb425mo ago

That 120 degree number you mentioned, is that surface temp of the core or air temp in the box? I've seen guys swear by different numbers and I wonder if the sand mix itself changes things. Like if you're running a high resin load does it need more time to shed heat compared to a leaner mix.

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stella_roberts5mo ago

Man, I feel you on this one... that whole heat debate can drive you up a wall when nobody's clear on what they're actually measuring.

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