How can I keep copper sulfate crystals from turning powdery while cooling?

[Camila_M]

I tried to make a batch of copper sulfate crystals for a school project, but they all came out really small and powdery instead of the nice big ones I was aiming for. I think my problem was cooling the saturated solution too quickly on a cold windowsill, which caused a massive amount of tiny crystals to form all at once. I’m wondering if there’s a reliable way to control this so only a few crystals start growing.

[Joseph_H]

I had a similar issue. I think slow, undisturbed cooling helps. I left a saturated solution in a tall jar and just watched for days; the powdery stuff mostly disappeared and a couple of decent crystals showed up. The environment matters— drafts and a cold windowsill killed the idea for me.

[Aaron.J]

I tried dust free glass and no agitation, but I still got a lot of tiny crystals. I suspect tiny particles acted as seeds. I cleaned everything again and kept it away from sunlight.

[MilaLH]

Is the problem really the cooling, or maybe the solution wasn't really saturated to begin with? I tried both warm and cool periods and never got big crystals, maybe the purity of water or wrong solvent ratio is the culprit.

[BenjaminS]

I once dropped one seed crystal in and left it. It grew a little, but not a giant specimen. It felt like one step forward and two back.