Old Yellow!

I had always been told that the reason boards yellow when they are dinged and not fixed right away, is because of the foams exposure to water over time. However, I was talking about ding repair with a friend and he said that he had recently heard that it is not the water that turns the foam around a ding yellow, it is the foam’s exposure to and absorption of oxygen. I have used plenty of old blanks in the past that had changed to a yellowish brown color, and when you skin them they are white, so I guess it kind of makes sense. But what about finished boards (who are sealed from oxygen) that have never been ridden that have been place in some storefront that turn yellow from the sun? Are these factors unrelated? Anyone know anything about this?

i know that the fiberglass itself turns yellow too. i’ve stripped the glass off of a couple of boards and the foam wasnt nearly as yellow as the glass was.

You are describing two different deals. Dings allow seawater into the blank and the residual minerals, salt and plankton cause browning of the foam around the ding. Cured clear polyester resin or epoxy resin will yellow when exposed to U.V. over an extended period of time. Unprotected will polyurethane foam yellow as well.

I want to echo steve page’s comment. a few years ago, I sanded down a 4-year old (plain white) board, and was surprised to find that the gloss and sandcoats were substantially more yellow than the foam - below - had become! the thing looked great after a new suit!