"FYI, smooth-on says that they wouldn't recommend dying the epoxy without doing tests first and use dye sparingly. ... Having said that, they don't test what they don't use. They have told me that the bowyers know more about the glue than they do. Now, that comes from an individual and probably not the companies stance. "
What a bizarre thing to tell customers!?!?
So my take on this is an employee at Smooth-on, who does not use their products, recommends doing tests on how much Smooth-on colorant to use in Smooth-on epoxy. Sounds like a good idea. You could always follow the manufacture of both products (Smooth-on) directions;
Even if their employee won't vouch outright for the efficacy of what he does not use, I will.
Been mixing Smooth-on colorants into smooth-on and other brand epoxy's for years with not one issue.
In fact you can use almost any colorant in epoxy as long as its not in a water or solvent based carrier.
That includes UTC's, alcohol based dyes and powered pigments, among a long list. Follow the manufactures directions, I guarantee someone has tested them or they would not risk selling the product.