I'm looking to cast a concrete tabletop with a particular pattern of deep, relatively wide grooves in the surface. The only cost effective material I know of in table-top sizes would be MDF, but it doesn't seem like it would be a very good choice for casting since it's so porous - especially the insides that would be exposed by cnc-carving. Is there any kind of mold-release that would work for MDF, and that wouldn't pool up in the grooves I'm carving? Or maybe there's some other kind of material available in large sheets that doesn't cost hundreds of dollars?
Thanks!