If you place the epoxy in direct sunlight, it will yellow over time. We add UV additive to our epoxy, so this effect does not happen as fast as other epoxies. However, this UV additive effects the color of the epoxy so if we add too much then the epoxy is no longer, "crystal clear".
This is the reason why we call it UV Resistant and not UV Proof.
Using Epoxy outdoors: If you want to use the product for use in direct sunlight, we suggest additional steps to protect the coating, such as applying a 2 part polyurethane as protection, after your project cures. Keep in mind, all epoxy will yellow overtime when exposed to direct sunlight, florescent, or incandescent bulbs, but including this process will help ensure you project stays crystal clear for years.