Rookie Sanding Resin & Catalyst Issue

I’m in the process of repairing my fish and decided to take on the repairs myself vs. going to the repair shop.  So between Sways and Youtube I was able to get most of the repair done but ran into a roadblock yesterday.  I was in the process of mixing 3 oz of sanding poly resin, q-cell, and 30 drops of catalyst, applied to the board but it didn’t harden.  I’m sure I should have not mixed in the late afternoon as it was 60-64 degrees with another hour left of sun but got antsy.  I’ve had the board in the backyard with direct exposure to the sun this morning and can feel the mixture slowly getting hard but assuming I pretty much botched this step of the repair.  So, I called the shop that I purchased the resin and he said just to mix a “hot batch” and paint on the repair and that it would “kick in”.  

Does that make sense or just scrape the batch, let dry, and restart?  What’s the recommendation on poly sanding resin per oz vs. drops of catalyst if its 65-70 degrees?  Does catalyst expire as the tubes I’ve had have been sitting in the garage unused for a few years?  Any recommendations on catalyst at Home Depot as it’s down the street vs. going back to the shop?


With low 60s as the starting temp and late day, you should have upped the catalyst by two or three drops per oz. You can just add another coat, or wait a while longer and see if it kicks completely before doing any more. Any MEKP liquid catalyst will work.  It can be found at auto supply shops, marine supply stores and other locations.

I doubt your catalyst went bad. I’ve used tubes that were 3-4 years old with no issues. Resin is another story,