Many epoxy resins on the market include a UV stabilizer (aka UV inhibitor) to help protect against yellowing, as well as other problems that epoxies are prone to (such as de-lamination, chalking, cracking and gloss loss). In truth, a UV stabilizer is necessary and effective, except when it comes to the yellowing issue. A UV stabilizer merely delays yellowing somewhat... another additive altogether is required to really combat yellowing— something by the name of Hindered Amine Light Stabilizer (HALS). Unlike UV light stabilization, Hindered Amine Light Stabilization (HALS) actually interrupts the yellowing process at the outset, making it much more difficult for yellowing to occur. HALS has been demonstrated in numerous test cases over the years to be extraordinarily effective in protecting against yellowing —there is approximately 50 years worth of this evidence available.