yellow patches in poly

[Hammer Ann]

I have never had this problem before. I am finishing a solid bench made with pine bead board applied to an MDF base. I had stained it to my satisfaction and so started to put on the protective satin poly finish, as I had done on many other projects. But as it dried, patches appeared in several different places; they looked like flaky, yellowish ecxema patches.

Well, thinking it was because I had used an old can of poly with an older brush, I did some repair work with sanding and oil paints, got out my new can of poly (gently and thoroughly stirred) and a different brush and went to work. Same result! The patches are now in other spots! This is the same brand of poly I have used for years without a problem, same technique, a tried and true brush (well cleaned), same garage. I have no idea what is going on. Any thoughts about what is causing this? And how to fix it?

[Harry72]

Im guessing there's either something in the wood causing the reaction, or are you using a type of grain sealer thats affecting the top coat?

[Hammer Ann]

I used the same progression of sealer, stain, and poly that I had used a dozen times before without a problem. I talked to somebody at my local homestore and she thinks it was the space heater in the garage cycling on and off. I don't remember if I finished with the space heater on before, maybe I didn't. I certainly won't do it again.

[Harry72]

I could understand the heat affecting it but only if the variance of temperature was above or below the temperature rating of the paint used...

[Hammer Ann]

Well, since the space heater was about 3 feet away from the surface....., We all do stupid things sometimes, don't we?