Thanks for this Forum. I will post a link on the Midwest Surfing Forum.

I hate throwing stuff away unused:

Now to the shelf life of traditional surfboard repair stuff: polyester resin and catalyst aka MERP. I have only found these quotes on the internet: "Because of the limited shelf life of MEKP, it is recommended that only enough be ordered for months use." "polyester resin only having an optimal shelf life of six months" Also, I was advised by my supplier to not order resin until right before I use it. Furthermore, another website said that once polyester resin freezes it is never the same.

Well, I have resin and catalyst from last summer. It was in a shed outside, so they probably froze several times over the winter. They both look just like they did last year. Yesterday, I brewed a batch. The resin hardened normal looking.

Heck, I may just use what I have for some repair patches and see it I can notice a difference in its performance.

On the other hand, someone once told me that I could use Acetone like paint thinner with resin. A chemistry friend told me, "NO!" that all acetone does it break down the polymers.

Still looking....

Bob,

You are welcome for the Forum.
I thought about having such a Forum when I first started this but decided to hold off. You gave me the reason to put one up.

Okay now for what I know about Resin.

If you want to thin Polyester Resin you will need Styrene Thinner. It is the only thing you can use on Polyester Resin that will not alter the chemical properties of it to much.

That is what "Air Dry" is made of, Styrene and a Wax additive. I have used Air Dry to thin finishing resin before in a pinch. I do have trouble storing Air Dry, if it's in a plastic container it seems to evaporate through the plastic causing a vacuum effect on the plastic container itself by sucking the sides inward. If stored in cold temps it will crystalize which I think is the wax turning to a solid again.

I have not heard of a shelf life for resin but it would only makes sense. I have had resin that is a few years old and I keep it tightly sealed metal containers stored at room temp, it still seems to be good.

I have also left Poly Resin outside in the garage and it has crystalized on me making it pretty much worthless.