This topic has been covered a bit in the past, but mostly 10-15 years ago. I'm wondering if there's any new theories on this that may have come to light in the ensuing years.
Basically I'm taking about the yellowing of Epoxy/EPS surfboards. This is not an issue I have encountered, but it appears that a number of people have. There is an interesting topic on the Swellnet site about it. https://www.swellnet.com/forums/wax/497925
Yeah so if anyone has a bit of time in their hands they might want to check out that topic and see what I'm on about. At any rate it'd be interesting to hear from someone who knows what they're taking about. I have absolutely no idea why this would happen. (the yellowing) My EPS/Epoxy boards are not in the faintest bit yellow, even after a number of years of use. They just stay white. I'm using pretty standard EPS and pretty standard Epoxy surfboard resin. I don't seal my blanks.