I've used wax-coated Dixie cups for several boats with no appearent problem. I see the potential problem coming when you stir and scrape the sides of the cup you might get little pieces of wax dust in the resin which could cause "fish-eyes" in subsequent layers of epoxy and varnish.

Waxless cups are probably better, but waxed cups won't make your boat implode.

> I thought I read somewhere (perhaps West System literature) that epoxy
> mixing cups should be wax-free, but System Three sells wax-coated mixing
> cups. I'd like to buy a large, cheap box of cups at the local warehouse
> store, but I wasn't sure if the wax would cause problems with the epoxy. I
> absolutely could not find any wax-free cups (except for the expensive ones
> at the boating shops). Anyone have any problems with generic wax-coated
> cups?