I know that with Devcon Epoxy, it does have a shelf life of about
two years. Not that it won’t cure, but it takes forever to do so.
It could be that you either have an aged product, or the product has
been switched to another manufacturer and the production standards
are not the same.
I suggest that if you purchased the Colores from Rio Grande and if
it is their product, then send a sample to their tech team and give
them the exact protocol you used plus a sample you made it from. You
can spend a lot of time trying figure out what happened, but time is
precious. Rio is a great company if there is a product that is not
working correctly, you can trust them to spend their time to research
your issue and solve the problem.
Folks, I cannot stress enough how important it is when you are
fabricating a piece of work, to DOCUMENT everything you are doing.
The design stage is one part, but the rest of the fabrication is
technical and requires good notes. When you run into a technical
problem, if the problem didn’t exist before, then your original
notes will come in very handy.