I have printed a mould in PETG to try and make a 5mm thick disc the size of a dinner plate. The mould consists of a top and bottom sandwiching the clear epoxy resin to be cast. I have sanded the surfaces of the mould right down to 3000 grit, so they are quite smooth, but I can't get a really good shiny finish. My transparent GlassCast 10 castings are not see-through, having a frosted appearance. My question is: is there something that I can coat the mould surfaces with that will give me a shiny finish, and hence a totally transparent casting, but will not bind the mould parts to the resin? I have tried the Easy-Lease Chemical Release agent and the Meguiar's #8 Mirror Glaze Release Wax, but still get a frosted surface. Applying an additional coat of epoxy resin after the casting has cured does make the surface more transparent, but its blurry, not at all like looking through a pane of glass, for example. Any thoughts?

I was wondering if, after printing a mould in PETG, I could coat it with XTC-3D to give it a smooth gloss finish and then cast epoxy or polyurethane resin in it? I'm assuming I would need a mould release agent as XTC-3D is epoxy-based and the casting resin would bond to it? Would "Meguiar's Release Wax" or the "Easy-Lease Chemical Release Agent" be sufficient to be able to demould the casting without impairing the gloss finish of the mould?

It is not always possible to get a high gloss off some plastics.  You could try coating the mould with an epoxy such as our XCR resin then sand it perfectly smooth and polish to a gloss.  The gloss mould should then give gloss parts.  Alternatively just polish the parts out the mould.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Thanks for the info Warren. If I coated the mould with XCR resin would it not bond to the casting resin?