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Discussion Starter · #1 · (Edited)
Hi all,

Here is what I did (all tools and material from HD):

1) Drum and edger sanded with 24;
2) Orbital sanded using 60 and 120;
3) Applied a coat of Minwax oil-based stain,
4) Did NOT apply sealer (the stain label read that it seals),
5) 1st coat of Parks oil-based poly using lamb wool applicator,
6) Waited about 8 hours,
7) 2nd coat,
8) Waited for about 12-14 hours,
9) Sanded with 220 paper.
10) Wiped off the dust. White streaks and spots remained. It looks like I didn't wait long enough, even though it was 80s those days and I established good ventilation in those rooms.
11) I went with advice I read online and proceeded with 3rd coat,
12) Waited about 8 hours,
13) Applied the 4th and last coat.

36 hours went by and disaster! It doesn't peel, but bubbly lines appeared in a few places, maybe total of 4-5 places. I think if I cut through the bubble, it would start peeling. It doesn't seem to be around the edges of the boards, just in random places here and there. I thought I applied thin coats, I relied on this technique: apply just enough poly so that the lamb wool moves without too much effort, but not more than that. I also looked at everything at an angle when moving to next section, to ensure no drops of poly left, etc. Also, it happened only in one room and I did the whole second floor, including 3 rooms and a landing area overseeing the staircase.

I live in Wakefield, MA. It is generally hot and humid, but hasn't rained while I've been applying poly, sunny almost every day.

Help please??... :) How do I fix it? What did I do wrong?
 

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4.)When it said it seals, that was false advertising. It just has a some linseed oil in it that partially seals
the wood. Sealer would make the job easier but was not necessary. Sealers have a lot of solids in
them which build the thickness quicker and are also formulated to be easier to sand.
6.) I think 8 hours drying time is rushing any oil based finish. I would have given it 24 hours and the
consecutive coats with only 8 to 14 hours drying time I think is your problem. It's just building up
solvents under the finish and not drying correctly and the underneath is shrinking wrinkling the outer
coat. It's white because the outer film has lifted completely off the previous coat.

There are a couple of different solutions. Let the finish dry a month and then take 220 sandpaper with a block of wood and sand the wrinkles out. This will probably leave a void where you will have to add finish in layers until you level the finish and then put another coat over the entire surface. The easiest and quickest would be to use a methylene chloride paint and varnish remover and strip the finish off and start over. Just be sure to thoroughly rinse the remover off because removers contain wax that will interfere with the new finish.
 

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I had something similar happen last year, but I think mine was from too many coats and I didn’t wait long enough between each coat. I’m just guessing because I don’t have any scientific information to back it up.

One other bit of information is when mine happened it was cold on the first few coats and then we had a heat wave on the last few coats. I don't know if that had anything to do with it or not.
 

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Discussion Starter · #4 ·
Thanks for quick replies. :thumbsup:

6.) I think 8 hours drying time is rushing any oil based finish. I would have given it 24 hours and the
consecutive coats with only 8 to 14 hours drying time I think is your problem. It's just building up
solvents under the finish and not drying correctly and the underneath is shrinking wrinkling the outer
coat. It's white because the outer film has lifted completely off the previous coat.
Again, the poly can says wait 16 hours if you want to sand, and less if not. It seemed that there were 2 options: don't let it properly cure and apply the next coat so that they bond due to "tackyness" of the previous coat; or wait 16 hours (I may have rushed by sanding after 13-14 hours, but I had a good family-related reason to hurry) and then sand and let the sanding roughness do the bonding. I figured I have to sand at least once, to get rid of the small bubbles, etc. Now I'm wondering which coats lifted of what: all 4 off the wood, the 2nd one of the 1st, or the last one off the 3rd one...

There are a couple of different solutions. Let the finish dry a month and then take 220 sandpaper with a block of wood and sand the wrinkles out. This will probably leave a void where you will have to add finish in layers until you level the finish and then put another coat over the entire surface. The easiest and quickest would be to use a methylene chloride paint and varnish remover and strip the finish off and start over. Just be sure to thoroughly rinse the remover off because removers contain wax that will interfere with the new finish.
I like the wait a month and sand/refinish option more :) Does it make sense to work on each bad area individually? Or designate a square area, say, 4' x 4', which covers all of the imperfections, and redo that area only? Or just redo the whole room (as I said, this only happened in one room)?
 

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Discussion Starter · #6 ·
PS. Re. only waiting 8 hours before sand-less coats: I read somewhere that oil-based poly dries inside out. After 8 hours, I was able to (carefully, of course) walk over the finish without causing any distress on the finish whatsoever. That made me thing that the poly is plenty dry to apply next coat; my thinking was that if oil-based poly dries inside out, then certainly when outside is dry to the touch, if not completely cured for usage (furniture, foot traffic), the next coat is in order. Again, this is based partially what I read online about polyurethane finish and what the can says - both notoriously unreliable sources of information... :smile:
 

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Often it's really difficult to tell if a finish is completely dry. Sometimes I will press my thumb really hard into the finish and see if it leaves a thumbprint but that is usually when the weather is cold or damp. I just wait 24 hours in good weather between coats to be sure and sometimes when the weather is bad leave it longer.

The drying process on poly starts with the solvent evaporating. Then the resins form a chemical reaction and harden into a plastic. Personally I don't believe in 8 hours the solvents were done evaporating. Then when another coat is put on the solvents in the second coat will hault the hardening process of the first coat. When the finish hardens it shrinks so if you put three or four coats on too soon before it shrinks that much then the last coat has to shrink more than it can and wrinkles. I think this is what happened. It could also be that you applied a thicker coat of the finish then the manufacturer intended however the only urethane type coating I would recoat that soon is one that has a isocyanate hardener forcing the chemical reaction.

It will take a full month for the finish to fully cure all the way to the wood is why I suggested waiting a month. What I expect to happen when you work on it is when you sand it, the sanding will more or less shave the wrinkle off of the surface. I expect when you clean the dust off you will find what looks like a gouge in the finish as if it was scraped. Using a small artist paint brush I would put as many coats of finish on the gouge until you fill it level with the rest of the floor, more or less using the finish like clear putty. Just put normal coats on in as many coats as it wants. Because of the drying time I would do all of them at once. Eventually you will get enough finish on the spots to brush a bigger area sanding between coats until you can't really see them any more. When you get it to that point scuff sand the entire floor and put another coat over all of it and you should be done.
 

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Discussion Starter · #8 ·
Often it's really difficult to tell if a finish is completely dry. Sometimes I will press my thumb really hard into the finish and see if it leaves a thumbprint but that is usually when the weather is cold or damp. I just wait 24 hours in good weather between coats to be sure and sometimes when the weather is bad leave it longer.
Does that 24 hour waiting period imply that you lightly sand before next coat, every coat?

The drying process on poly starts with the solvent evaporating. Then the resins form a chemical reaction and harden into a plastic. Personally I don't believe in 8 hours the solvents were done evaporating. Then when another coat is put on the solvents in the second coat will hault the hardening process of the first coat. When the finish hardens it shrinks so if you put three or four coats on too soon before it shrinks that much then the last coat has to shrink more than it can and wrinkles. I think this is what happened. It could also be that you applied a thicker coat of the finish then the manufacturer intended however the only urethane type coating I would recoat that soon is one that has a isocyanate hardener forcing the chemical reaction.
Good to know. I doubt Parks Pro stuff has that hardener.

It will take a full month for the finish to fully cure all the way to the wood is why I suggested waiting a month. What I expect to happen when you work on it is when you sand it, the sanding will more or less shave the wrinkle off of the surface. I expect when you clean the dust off you will find what looks like a gouge in the finish as if it was scraped. Using a small artist paint brush I would put as many coats of finish on the gouge until you fill it level with the rest of the floor, more or less using the finish like clear putty. Just put normal coats on in as many coats as it wants. Because of the drying time I would do all of them at once. Eventually you will get enough finish on the spots to brush a bigger area sanding between coats until you can't really see them any more. When you get it to that point scuff sand the entire floor and put another coat over all of it and you should be done.
Yep, I heard that 30 days is normal time to wear for complete drying. I'll post results when I get to do that in a month.
 

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Any polyurethane has adhesion problems built into it so I would recommend sanding with 220 or finer grit between coats. The scratches the sandpaper makes gives it something to bond to. It's possible that the finish you did might not have wrinkled if you had sanded it between coats.

You would have known it if the Parks finish had the hardener. It would be something you would have to mix as you were using it and any finish left over after mixing the hardener would go bad in the can.
 
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