I have been fusing float glass and make my own clay molds. I would like to sprinkle sand on the molds to create indents (texture) on the bottom of the glass piece when it slumps. I don’t know what kind of sand to use or where to find it. Would regular play sand work, or maybe white sand?
I think this is one where experimentation is required. Let us know the results. All of these sands mentioned have a high level of silica in them and may stick to the glass. This can be reduced by dusting talc (bad for your health) or alumina hydrate over the sand.
It occurs to me that you may get a similar result to sand, by sprinkling powdered batt (kiln) wash onto the mould.
You can just sprinkle Kaiser Lee Board powder on your molds. It is reusable many times and will work great with float glass. I can mail you a bag of it for shipping and handling costs. Just tell me how much you want. What are you using to make your molds?