Epoxy granite metal lathe - videos

[tonyfoale]

...... you will need more epoxy the more surface area there is in the mold. The large aggregate doesn’t pack well against walls and other features, so you end up needing slightly more epoxy to not have voids.

Voids on the surface are a cosmetic issue only, you should not compromise the bulk to the needs of appearance. It is easy to get a nice finish after mould release by filling the surface with a resin and glass micro-balloons mix.

So if you add like a 1/4in wire mesh inside the mold, you add a lot of surface area and small features, which would dramatically increase the epoxy you’d need in my experience. Personally I might put like rebar or threaded rod in the mold as the steel framing, but Id probably stay away from mesh screens (the surface roughness of the rods/rebar shouldn’t effect the epoxy too much more than a smooth rod and getting a mechanical grip from the epoxy is always nice)

I would stay away from any mesh, that makes it way too hard to avoid voids. Rebar set in along the length of the casting is a good method but I would sand blast it first and maybe paint it with neat resin just before casting. I see that several people advocate using a fast cure hardener, I go the other way and use the slowest hardener. Apart from the time benefits of working with a slow set, the exothermic reaction will significantly heat a large casting during a fast cure. If the cure takes 24 hours then the heat has so much time to dissipate that the temperature rise is very low, which results in a more stable casting.