|Forum topic by Sandro||posted 05-08-2010 02:44 AM||12591 views||0 times favorited||5 replies|
05-08-2010 02:44 AM
I am painting an old wooden handrail. I gave a couple of coats of stain and a couple of coats of polyurethane. I waited at least 24 hours between each two coats. Everything went well until I decided to give yet another coat of polyurethane. That polyurethane immediately turned white in several places.
I have read that humidity causes polyurethane to turn white. However I didn’t use any water, and I believe the humidity level in my garage is pretty normal. I used one brush for the stain and a different brush for the polyurethane. I clean the brush with thinner each time and save it inside a zip-locked plastic bag wrapped in a paper towel moistened with thinner, so it doesn’t dry.
Could the thinner remaining in the brush have caused the problem? Or is water the only thing that makes polyurethane turn white? And why did this happen only once?