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white crusty bubbles in shellac/poly help the newbie

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Forum topic by droppedtuning posted 06-04-2015 05:55 PM 1006 views 0 times favorited 14 replies Add to Favorites Watch
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droppedtuning

31 posts in 1585 days


06-04-2015 05:55 PM

please help the newbie. building a fireplace mantle from pine. the whole surface was scrub planed for texture , then grained was raised then knocked down. i sprayed transtint waterbased dye on it. let it dry a day then two coats of bullseye dewaxed sealer on top of that. i scuff sanded after each coat had dried a day. yesterday i did one coat of 50/50 minwax oil poly and mineral spirits . today i have a white crusty disaster. i know moisture will turn poly white at times although this was thinned half down and wiped off single coat but bubbles and crusty rough ? please help the newbie ? thanks guys !https://s3.amazonaws.com/vs-lumberjocks.com/npflrms.jpg!


14 replies so far

View firefighterontheside's profile

firefighterontheside

16482 posts in 1641 days


#1 posted 06-04-2015 05:57 PM

Exactly which poly did you use?

-- Bill M. "People change, walnut doesn't" by Gene.

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hotbyte

987 posts in 2760 days


#2 posted 06-04-2015 05:58 PM

Weird. Did you shake the poly vs stirring? I’ve always heard to never shake it or it will get air bubbles. So, I never have. I don’t know if that is what the air bubbles would look like.

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droppedtuning

31 posts in 1585 days


#3 posted 06-04-2015 06:01 PM

stirred not shaken

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bobasaurus

3299 posts in 2969 days


#4 posted 06-04-2015 08:03 PM

It must be the mixing of finish bases, though the shellac should have helped. Was the shellac dewaxed? If not the poly won’t stick on top of it. Try sticking to all water based, or all oil based dyes/sealers/finishes.

-- Allen, Colorado (Instagram @bobasaurus_woodworking)

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chrisstef

16863 posts in 2791 days


#5 posted 06-04-2015 08:19 PM

I think you’ve got moisture trapped under the poly film. Maybe the mineral spirits weren’t mixed well enough in with the poly and in some spots there was more spirits than poly and it never got enough time to evaporate fully. I doubt it was the shellac. Id sand it back and go full strength with the poly, possibly a new can.

Was it the fast dry poly?

-- Its not a crack, its a casting imperfection.

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MrUnix

5819 posts in 1984 days


#6 posted 06-04-2015 08:19 PM

Lots of different solvents used there… so it’s got to be a bad interaction. The dye is alcohol/glycol based with water. The sealer is ethanol based, and the poly was mineral spirits. A finish like you got usually results from not letting the lower coats of whatever flash off the solvents, and mixing/matching like that usually requires making sure that they are completely dry and all the off-gassing is done. Bummer, but you will need to take it back down to bare wood and try again… perhaps waiting a bit longer between steps if you choose to go the same route.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View Fred Hargis's profile

Fred Hargis

4651 posts in 2278 days


#7 posted 06-04-2015 08:45 PM

It’s not obvious to me what caused that, certainly nothing in the schedule you followed seems wrong. Let me ask about the mineral spirits, it wasn’t one of the new “green” formulas, was it? As much as I dislike Minwax anything and would like to blame the oil based varnish, I don’t think it would have done that.

-- Our village hasn't lost it's idiot, he was elected to congress.

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firefighterontheside

16482 posts in 1641 days


#8 posted 06-04-2015 08:59 PM

It wasn’t the oil modified poly was it? I don’t think that would be miscible with mineral spirits.

-- Bill M. "People change, walnut doesn't" by Gene.

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droppedtuning

31 posts in 1585 days


#9 posted 06-04-2015 09:34 PM

i followed transtints website directions. i wiped mineral spirits over it and nothing. dewaxed shellac yes

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droppedtuning

31 posts in 1585 days


#10 posted 06-04-2015 09:36 PM

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Bill White

4769 posts in 3745 days


#11 posted 06-04-2015 10:04 PM

Was the wood dry, prepped in the sun?
I’ve seen and experienced that effect from using or drying outside on a sunny day.
Bill

-- bill@magraphics.us

View gfadvm's profile

gfadvm

14940 posts in 2475 days


#12 posted 06-05-2015 12:29 AM

Like Bill, I have had this happen when I thought putting it out in the sun to speed drying was a good idea. NOT! Other than that, I have no idea why it happened.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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droppedtuning

31 posts in 1585 days


#13 posted 06-05-2015 03:38 AM


i gave up and hit it with stripper and alcohol. now i have to figure out what to do with the dye

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chrisstef

16863 posts in 2791 days


#14 posted 06-07-2015 08:49 PM

Dont thin the poly and i bet youll be all right with your original finush schedule. There’s a drying agent as well as flatteners in the satin fast dry poly. Id bet theyre all acting against each other when you introduced more mineral spirits to the equation.

-- Its not a crack, its a casting imperfection.

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