TIL I was wrong about using just bentonite for green sand in our small shop.

For years, I'd mix our molding sand with 8% bentonite and a bit of water, thinking more clay meant better strength. Last month, a guy from a big shop in Toledo told me he adds 2% seacoal dust to his mix. I tried it on a batch of simple cast iron brackets, and the surface finish was way smoother, with way less burn-on to clean up. Has anyone else made a switch like that and seen a real difference in finish quality?

3 comments

3 Comments

maxb462mo ago

Maybe for simple brackets, but that seacoal trick can backfire on more complex molds. It creates gas that can cause pinholing if your venting isn't perfect. I've seen it ruin a whole flask.

grant4652mo ago

My uncle lost a whole set of gear sprocket castings that way back in '92. He swore off seacoal for good after that. What do you use for your complex molds instead?

theas941mo ago

Funny how the same logic applies to cooking, one wrong move and the whole dish is wrecked.