What is causing this poor refinishing result and how do I fix it?

Question

I followed the procedure of stripping, sanding, staining and then polyurethaning the top of two antique, about 75 years, dressers. The one came out beautifully. The other has questionable results.

There was an area of the one dresser that had what I believed was water damage. It is unknown if my conjecture is correct, but that would be the most logical answer. I got the old varnish off with citra strip. The area of the suspected water damage was discernable but not egregious. I then sanded the top to a silky smooth texture. Due to the age of the dresser I suspected that there was a veneer on the top so I used 150 then 220. Both sanding steps were on the easy does it scale. The tops were silky when done.

I stained both twice for 10 mins each time to get correct color. When I applied the Minwax Fast Drying Polyurethane Clear Satin to the one dresser it seemed to almost 'bead like water' in the area of the former stain. When dry, there was a textural difference in that area. I was hoping that it would self correct with the light sanding and the application of a second coat. It only got worse.

I am obviously going to remove the poly and try again. What could be causing this problem? Can it be prevented from happening again? Also, in between all the steps, I used tacky cloth to ensure that the tops were free of debris.

Answer 1

Fine sand for a new start. Then coat with a full gloss yacht or spar varnish then sand and recoat every 24 hours until you get the desired build. Yacht varnish builds quicker than polyurethane and behaves more predictably.

Then I would lightly sand with flour paper (2400 grit) and then apply two coats of polyurethane to give durability. Apply the second coat at the nominal drying/recoat time, don't let it go too hard.

The yacht varnish will fill any dents and is not too particular about contamination whereas polyurethane has skittish moments and sometimes will actually flow out of small depressions on its second coat because of some weird surface tension effect. This is really weird when it happens - you pour paint in but the dent never fills.