removing polyurethane from wood - Woodworking Talk - Woodworkers Forum
 
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post #1 of 16 Old 02-02-2013, 08:44 PM Thread Starter
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removing polyurethane from wood

I have a wood box that a family member helped build, and he sprayed it with a can of spray polyurethane, which he sprayed on many times, creating a shiny coat. Well, I'm redoing it now, because my wife doesn't like the coating. I started by sanding off the bulk of it. But now, in the small grooves in the grain (the box was not polished much), there remains bits of shiny polyurethane. I want to get rid of it.

So, this whole process has been a learning process. At Home Depot, they told me I could use Low Odor Mineral Spirits, and apply it with a tack cloth, and use a small bristle brush to rub in the direction of the wood grain. (I bought a 3-pack of handheld brushes, one being nylon, one some kind of softer metal wire, and one being a steel wire brush.)

I tried this, wiping on mineral spirits, and then using the softer metal wire brush. (I briefly tried the steel wire brush, but found it took off much wood in the process.)

But now, as it sits drying, I see the polyurethane remains. (Though some of the Titebond wood glue has come undone at certain joints...awesome.)

So, what should I do?

1) Get something stronger? (If so, what? Prefer something as nontoxic and nondangerous as possible. I don't have a shop to work in.)

2) Go back with mineral spirits and use the steel wire brush?

3) Something else?

Thanks for reading!

PS: Next steps, sand it a bit, as the walls of the box are not entirely flat; rebuild the lid from spare matching wood; finish.

Last edited by frozenbase; 02-02-2013 at 09:40 PM. Reason: typo
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post #2 of 16 Old 02-02-2013, 08:53 PM
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What finish do you plan to put on it? Could be that your new finish will cover the "shiny" quite nicely.

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post #3 of 16 Old 02-02-2013, 09:30 PM Thread Starter
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It's walnut, so I want to protect it but keep it as close to raw wood looking as possible. I have no idea though. One local guy (at a handmade furniture store) was telling me about some oil I could use. I don't want it shiny.

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post #4 of 16 Old 02-02-2013, 10:20 PM
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You don't want to put oil on top of poly remnants, but a very low-gloss poly would work just fine. It will cover the shiny remnants and produce a non-glare surface.

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post #5 of 16 Old 02-02-2013, 11:00 PM Thread Starter
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But if I want to go with the oil method, how do I get rid of the poly remnants?
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post #6 of 16 Old 02-02-2013, 11:06 PM
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There are two things that you can buy at the home center that should remove the polyurethane.

Lacquer thinner and MEK. (Methyl Ethyl Ketone) Both products should be used outdoors with a lot of ventilation. Both are very flammable but MEK can be ignited by a cigarette. MEK is generally very nasty stuff.

Start with the Lacquer Thinner and use a squeeze bottle to wet the project. Use a rag to keep the project wet with the Lacquer Thinner. In a few minutes you should be able to wipe the poly out of the grain of the wood.

Use the right tool for the job.

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post #7 of 16 Old 02-02-2013, 11:55 PM Thread Starter
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Thanks for the reply. Will my latex gloves be okay to wear while using lacquer thinner, or will they melt from it? Any similar concerns with a plastic squeeze bottle?
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post #8 of 16 Old 02-03-2013, 09:43 AM
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The best thing you could have used to get the polyurethane off is a methylene chloride paint remover but it certainly wouldn't make the nontoxic, nondangerous criteria and are quite the opposite. There is a citrus remover that is a lot safer but a lot less effective. Since you have sanded most of the old finish off unless you plan to use stain the piece I would just sand the poly in the grooves smooth and finish over it. The shine can be killed with coating over it with a semi-gloss or satin poly. The low odor mineral spirits is going to do absolutely nothing to the poly. Even regular mineral spirits is so mild it's not going to do anything to dried polyurethane. I would advise you to dispose of the low odor mineral spirits before you end up trying to thin some paint or poly with it. The stuff isn't good for anything. Lacquer thinner will lift the poly but is a little labor intensive. You will need chemical gloves to handle it. The thinner will go straight through exam gloves. Regardless it would be a good idea to wash the piece down with lacquer thinner to get any residue of the low odor thinner mineral spirits off of it.

Keep in mind if you choose to use paint strippers temperatures below 70 degrees they practically don't work.

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post #9 of 16 Old 02-04-2013, 03:09 PM Thread Starter
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Okay: here's where i'm at: I got the Lacquer Thinner, and some cotton rags, and chemical gloves. I put generous amounts of thinner on the rag, put it on the wood, and watched it evaporate quickly (it's 73 degrees here). Seeing no results to the shiny poly residue in the grain, and having not gotten a squeeze bottle, I proceeded to carefully pour the Lacquer Thinner in to a small pool on the area I was working on. In this manner, it didn't evaporate very quickly, and I waited until it started to, and then I rubbed it down with the rag. And still, the poly residue remains in the grain.

Meanwhile, two days after using the mineral spirits, it still seems that the wood has streaks of wet areas: mineral spirits residue perhaps as the previous poster (Steve) mentioned? It doesn't feel wet.

So, what's the best way to proceed? Wash it down with lacquer thinner to remove the mineral spirits residue (hopefully), then proceed to using something nastier? Or use a different technique with the lacquer thinner (such as putting it in a pan, and setting the wood to soak in it)?

Last edited by frozenbase; 02-04-2013 at 03:12 PM.
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post #10 of 16 Old 02-04-2013, 04:11 PM
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I think you would save yourself a lot of misery by just getting a can of Kleen Strip paint and varnish remover and stripping the piece. It's not that much more harsh than lacquer thinner as far as handling it. You will still need to wear chemical gloves. The most important thing is use the stripper outdoors where you can stay upwind from the fumes. Try as best as you can not to breathe the fumes as it contains a cancer causing agent. 15 minutes and it will lift the finish where you can scrape it out of the grooves with a brass pot and pan brush. It is important to rinse the residue of the remover off after you get it stripped. Normally I recommend rinsing this residue off with water but since you have it mostly stripped anyway, I think lacquer thinner would be best for this purpose.
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post #11 of 16 Old 02-04-2013, 11:52 PM
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That is odd. I've used lacqure thinner to remove poly many times. It get's soft and then just sort of wipes off.

Use the right tool for the job.

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post #12 of 16 Old 02-05-2013, 03:15 AM Thread Starter
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Thanks, I'll try the stripper. I'm going to go w/ the spray can since it's a small project: http://www.wmbarr.com/product.aspx?catid=72&prodid=112

Thanks for the warning on the carcinogens. Fun fun.

Will the clean up wash with the lacquer thinner help eliminate the wet look let in streaks in the wood, which was left over from the mineral spirits attempt?
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post #13 of 16 Old 02-05-2013, 03:17 AM Thread Starter
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Quote:
Originally Posted by rrich View Post
That is odd. I've used lacqure thinner to remove poly many times. It get's soft and then just sort of wipes off.
I'm not experienced with this stuff, but maybe it has to do with the thinner evaporating too quick, or maybe not getting into the wood grain to the back side of the poly, since this is hardwood walnut? Just tossing out random theories, given I don't know much about this stuff. But at least I still have a use for the thinner in the after wash step
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post #14 of 16 Old 02-05-2013, 07:46 AM
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Quote:
Originally Posted by phinds View Post
You don't want to put oil on top of poly remnants, but a very low-gloss poly would work just fine. It will cover the shiny remnants and produce a non-glare surface.
This is IMO, the best suggestion.I would just scuff sand the finish, and recoat with a low gloss/satin poly.

I would not use mineral spirits, as it would be useless. There's more to finishing and refinishing than just getting a finish on. The steps and what is used can be of benefit, or it can be your worst nightmare. There may not be an initial reaction, but a new finish could be at risk of failure. Using lacquer thinner as a stripper will dissolve the poly and allow it to seep into the grain as a very thin mix. You will likely not get it all out.

If you are going to remove the finish, use a good MC based (methylene chloride) stripper. The best over the counter stripper I've used is "Aircraft Stripper" in a blue can. It will remove the finish and hold it in suspension until it is removed. When all the applications of stripper have been applied, and as much of the old finish has been removed, at that time lacquer thinner can be used to wipe up the remaining residue.






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post #15 of 16 Old 02-18-2013, 01:54 PM
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I've been in the same boat before, I refinished an oak table once and put down some high gloss poly, the glare was unbearable. I sanded it down and still had shiny spots in the open grain. I used a satin poly and it came out great. So as long as you want to use poly, I wouldn't worry it.
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post #16 of 16 Old 07-10-2017, 06:22 PM
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I used a high gloss floor finish on my ceramic tile floors.It looked wonderful and shining but the next time I mopped with regular cleaner it became foggy whit streaks everywhere. I tried vinegar and it just made it worse and did not remove. The high gloss solution I used as polymer as the main ingredient. any ideas on which product will remove? Thank you.
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