Blistering heat and blistering varnish.

[lowangle al]

I was back East last month during a heat wave and all three of my w/c boats got some blistering of the varnish on their floors. Could it have been the heat, or is something else going on? I doubt it got over 90 F and I kept the boats flipped over when not being used. The couple of blisters I scratched open exposed varnish and not wood so I think I'll leave it alone for now, but will the blisters cause me more sanding in the future?

 

[deerfly]

Yeah, could be. The weird thing here tho is you say there is varnish underneath the blistered coat so its probably not from the heat drawing moisture or oils out of the wood below. Maybe some trapped moisture between to two coats and the heat expanded the moisture to the point where the outer layer of varnish was pushed up. Could be some other type of contamination underneath the top coat too.

Either way my crystal ball predicts some scraping, sanding and refinishing in your future

 

[lowangle al]

I had sanded and added a couple coats of varnish to two of the boats at the same time in the same conditions and one of them has hardly any blistering compared to the other two. The boat with the least amount of blistering spent the least amount of time on the water so maybe it happened when they had direct sunlight on them. The boats were stored in a pretty humid basement, could that have an effect?

Whatever the case may be I think I'll wait until the varnish starts to wear thin before I redo it. That way there will be less sanding and it will be way down the road. Thanks for your reply Deerfly.