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So I recently bought a piece of furniture which (based on my research) has a polyurethane finish. After it arrived I discovered it had scratches, which I believe is polyurethane flaking off (you can flake it off/scratch it with your fingernail really easily). They are only surface scratches and don't go into the wood however.

How would I go about removing the surface scratches? I've seen articles suggest either sanding the entire polyurethane finish and applying another coat or sanding, applying a finishing wax and using 0000 steel wool to polish.

I know nothing about woodworking and I'm not sure what article to believe so was hoping to get some helpful advice.

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  • Hi Eric, welcome to woodworking. As you're an experienced SEer I have no hesitation in asking, did you try a search first? We have quite a few previous Q&As here which basically cover the issues here + what you can/should do here. Based partly on A, are dealing with polyurethane? You want to actually check to confirm this since the previous finish type is critical to knowing how to proceed (educated guess but I'd say this is unlikely to be poly), and B, depending on what level of finish you're hoping for on the completed project. You make have to completely refinish for a really good result. – Graphus Sep 11 '20 at 8:33
  • "I've seen articles suggest either sanding the entire polyurethane finish and applying another coat" Discount that. And while you're at it be a bit dubious about anything else from the same source. Existing polyurethane is rather famous for being impossible to repair, invisibly at least. While that exaggerates the case somewhat the fact is that once you get actual losses — where you're back to bare wood — there is nearly no option but to strip and refinish. Note this is on the affected surface, not the entire piece of furniture necessarily (depending on the condition elsewhere). – Graphus Sep 11 '20 at 8:34
  • Thanks @Graphus, I appreciate you taking the time to respond! I did search, but I was unsure on if I was really searching for the right things and the answers I did find didn't mention peeling. I guess I'll just have to live with it for now as a refinish sounds like it requires access to tools I don't own. – Eric Sep 11 '20 at 15:24
  • Also out of curiosity, besides poly what would your guess be that it is finished with? All I know is it has a gloss finish. Also any idea what would cause the finish to flake/peel off? – Eric Sep 11 '20 at 15:26
  • If you search for peeling specifically you should find a couple of Q&As, e.g. woodworking.stackexchange.com/questions/9910. There's a good chance this is finished in a type of lacquer. What kind used to be an easy guess, since nitrocellulose lacquer was used on nearly everything. Now with all the concerns about being green and not using high-VOC finishes it could be anything, including some waterbased lacquers — "lacquers" I should say, since they're not lacquer really. If it's varnish, then it's likely it's a two-part varnish, AKA conversion varnish, which can include urethane. – Graphus Sep 12 '20 at 7:45
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It will not be easy to fix that. There are a lot of different kinds of polyurethane formulations. It is probably a thermoplastic, meaning no solvent is going to work.

You can try using acetone on the edges.

The other thing you can try is to get an iron and a thin cloth and then carefully iron over the spots using the swatch of cloth as a protector.

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In the past when I've done this kind of thing I found that "paint stripper" chemicals were overall an easier approach than sanding or scraping right off the bat. Strippers like that are generally formulated to break down, loosen, or somewhat dissolve many different types of finishes, not only paint.

The general method is to apply a coat of stripper with a brush, wait a bit (15-20 mins?) while it reacts & bubbles, and then basically scrape it all off with a putty knife into the trash. Some disposable towels and sometimes steel wool or a scratchy plastic kitchen sponge can be used too. But you don't want to use a lot of force, when the easy stuff is done coming off, apply another coat.

I'd guess after 2-ish coats the finish would be gone. At that point you would want to wipe the surface clean (maybe just with water) after which you can sand & refinish essentially like it was new wood.

Paint strippers are widely available and I would make sure to follow whatever directions they come with.

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