Changed my mind about using a wet rag to cool a mold

I was in a rush on a small bronze pour last week and hit the sand mold with a damp cloth to speed things up, which I've seen old timers do. It cracked the mold face and ruined the piece, so I guess that 'trick' only works on certain mixes. Anyone know the exact sand-to-water ratio where this stops being a good idea?

3 comments

3 Comments

cooper.reese3mo agoMost Upvoted

What kind of sand mix were you using?

river_fox183mo ago

That 60/40 sand to cement ratio you mentioned, @cooper.reese, did you find it held up well or was it too brittle?

caseyrivera2mo ago

honestly nobody's talking about how the type of sand matters way more than the ratio imo. like if you're using playground sand vs mason sand vs crushed rock fines it changes everything. playground sand has too many round grains that don't lock together so even at 60/40 it'll crumble. i've had way better luck with angular crushed sand from a concrete supply place, that stuff holds like velcro even at 55/45.