I'm having interesting problems with polyester resin and Loew's underlayment 5mm Luan. If you've read my last few posts, I had an issue with some resin that I under-hardened. I have since that time, sanded down the "offending" resin, which had about 98% hardened by the time I got to it with the sander. I applied some additional resin, using the correct mixing ration, and had the same problem, both going over the first coat, and where it was applied to fresh, virgin luan.
Last night, I tried sample #3. I over-hardened the resin, and did a test area applying a thick (to the point of running) coat over fresh luan, resined, sanded and recoated luan, and resined, and sanded only luan. The thick resin cured in a normal amount of time, within an hour or so, it was hard and dry to the touch.
Something in the Luan is retarding the curing of the polyester resin. I checked the batch code on the resin with the manufacturer, and it is current product. I sell several hundred gallons of this product every year, so I know the quality is top notch also, and there are no bad batches at the moment.
Tonight's project will be to attack the cured thick spot of resin on the trailer, to see if I can separate it from the substrate at all. If it fails tonights test, my only option is to sand the entire trailer down again in about a week when it has dried/cured, and run some tests using a sealing primer like a urethane primer. If it passes tonight's test, it means i'll be adding a few weeks to my build schedule, since dry between coats for at least the first couple coats will be a week instead of an hour.
This has me very puzzled.
and frustrated.