Whats the IOR of Plaster?

Plaster, not plastic. :slight_smile:

Which is similar to gypsum and you can find the IOR for that here.
But I think it’s the reflectance more than the IoR that’ll make it look more plaster-ish and you can find that here. It’s actually called ‘plaster’ in that list.

Unless you need to be super accurate for some scientific reasons, 1.45 is a safe IOR for most normal dielectrics. Water should be lower, glass higher, diamonds even higher. Also note that most such lists can not be used for metals at all.

Ah, yes. It says Gypsium in that list so I thought it was talking about a different material.

What about Ceramic? I can’t seem to find the value for it anywhere.