I've been making small aluminum brackets for a project. The thin edges always get hairline cracks after they cool. I tried changing the sand mix and letting molds dry more. It didn't work. Then I remembered an old caster saying quick cooling causes stress cracks. So, I now bury the molds in dry sand right after pouring. This slows the cooling a lot. Since I started this, the cracks are gone. It's a simple trick that costs nothing. Has anyone else found ways to handle thin sections?
