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Discolored halo under clear finish - advise sought

3/1/16       
Gavin Member

Hi,

This may be a remedial question to some of you, but I'm wondering if anyone could help me solve a problem with a 'ghosted' area under clear waterborne finish on a sapele door. See photo.

I have already sanded this back liberally to bare wood, after spraying a first coat, and the problem has returned identically. Is this possibly oil contamination? It seems like the wood isn't wetting out. Would wiping it down with lacquer thinner or something after sanding down to bare wood help? If I sand it too much more, I'm risking sand-throughs. I really don't want to remake this door, as it's part of a row of doors made with the same board.

Thanks in advance for any information.


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3/1/16       #2: Discolored halo under clear finish ...
PainterDave Member

looks to me like maybe some water had set on the wood and left a ring in the grain...?

3/2/16       #3: Discolored halo under clear finish ...
Paul Snyder  Member

Website: finishing.tips

Gavin - is the milky colored ring caused by the finish losing adhesion to the wood or is something in the wood coming to the surface after you apply the finish? Is it always visible when the finish was removed?

3/2/16       #4: Discolored halo under clear finish ...
Gavin Member

Hello and thanks for the responses,

The ring was not visible before finishing, and it disappears completely upon sanding the wood. Then once it's sprayed, it slowly reappears as the waterbased lacquer cures. The adhesion seems to be fine, and the white areas aren't blisters. The symmetry of the stain makes me think it has to have been some sort of liquid, but water marks have never caused me problems like this. My latest guess is that it might be from saltwater from road salt that got on the sheet while it was being unloaded from the freight truck.

I'm thinking of sanding the whole panel down to raw wood, then scrubbing it with a damp rag and also with lacquer thinner. I might try making a sample salt stain and see if looks similar. Thoughts?

3/2/16       #5: Discolored halo under clear finish ...
Paul Snyder  Member

Website: finishing.tips

It sounds like there's something in the wood or under the veneer that's migrating to the surface. There's a very good chance that the water in the finish is causing it.

Sanding the surface of the wood only removes the whitish material that was deposited there - not the underlying source. Sealing the panel with a solvent based product before applying the waterborne finish could fix the problem (there's a chance it won't), but that will look different than the other doors.

It's possible that washing the area with lots of fresh water after you strip it may remove the source of the problem, but there's no guarantee.

I'd recommend replacing the door at this point.

3/8/16       #6: Discolored halo under clear finish ...
Gavin Member

As a conclusion to this thread, I'm happy to say I solved the problem, and thanks for the help.

I made up a test panel using brine to stain several areas, and gargled with the remainder. It indicated to me that the stain was indeed salt, or something similar which would form a solution in water, and washing it down with water solved the problem.

I sanded down the door to bare wood, then flooded it with water using a sopping wet rag. Then I wrung out the rag and scrubbed the affected areas. I did this mopping three times.

I hope this helps anyone else who finds themselves in a similar pickle.

3/8/16       #7: Discolored halo under clear finish ...
Paul Snyder  Member

Website: finishing.tips

Good outcome Gavin - I'm glad it worked.

Was it more cost effective to strip, wash, and refinish the door rather than make a new one? Or was that a factor?

3/10/16       #8: Discolored halo under clear finish ...
Gavin Member

Much faster to refinish. Although this is in relation to my speed at building doors, which is pretty slow...

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