Hi All,

I was given a low-cost surface plate (a granite kitchen countertop). I'm planning on using this flat surface at the bottom of the mold. I will screw linear rails to the resulting epoxy-granite bar.

To be able to drill and tap holes for the screws I'm planning this construction:

-Bottom layer (becomes the side with the rail after curing): pure epoxy
-Top layer: epoxy granite with columns of rebar, so I drill and tap into steel.

I have to cote the mold with a release agent, but that will introduce a non-flat layer between the surface plate and the epoxy.

Would a sheet of foil instead of the release agent work?
Would aluminum foil be a viable candidate? Does this have a uniform thickness?