Microballoons are tiny hollow glass spheres that look like confectioners sugar. So you won't be making them (G). They are used as a filler to lighten epoxy to make fillets. I have an old bottle from K and B Mfg. but I don't know if it is still available. There have been warnings not to ingest this stuff as it is as bad as fiberglass if it gets into your body.

Dave Segal