# Is it OK to sand polycrylic after final coat?



## jesseadams (Apr 9, 2019)

I am using old polycrylic and an older brush. I can't seem to avoid thick particles of poly and air bubbles. If I did 4 coats of polycrylic is it safe to sand with 400 grit sandpaper gently the after the last coat to smooth everything out? Is there a better approach? I'd really like to buff it out nice.

Thanks!


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## Steve Neul (Sep 2, 2011)

You would need sufficient finish to sand the finish and buff it. Without being there it's difficult to say. Polycrylic is awful thin and my instincts are that you don't have enough for that. A finish buffed would come to a high gloss. Is that what you want? Anyway when you sand to buff the sandpaper shouldn't be any more coarse than 1200 grit and then sand to 2000 grit. If the nibs are very pronounced I don't believe you can get it level enough to sand it with that fine grit. You would have to start with 400 and then 600 and then 800 and then you could go to 1200. It would take a great deal of sanding to rub out the abrasion caused by the 400 grit paper. Then what ever was contaminating the finish would probably leave a dull spot where it was. If it were me I would purchase a cheap paint sprayer and a fresh can of polycrylic. Sand it with 180 to 220 grit and put another coat or two fresh coats on and you would be done. If you still wanted to buff it you could sand it with 2000 grit and buff it. Keep in mind the finish should dry for a couple of weeks before any attempt is made to use a buffer on it.


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## sunnybob (Sep 3, 2016)

Surely new polycrylic and new brush would solve all your problems?


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## epicfail48 (Mar 27, 2014)

You technically _can_ sand it, but i wouldnt want to. If polycrylic works anything like polyurethane, which im 90% sure it does, conventional wisdom says that the finish will never get any smoother than off the brush. Reason being, polyurethane/crylic goes on in thin coats that dont meld with the previous coats, so any sanding on the top layer can cut through that layer into the ones underneath, leaving you with giant witness marks where the different layers meet. Another problem is that the finishes are designed to be durable, i.e resistant to scratching. Sanding, as everybody probably knows by now, its just putting finer and finer scratches in something, a method that isnt particularly agreeable on something that isnt supposed to scratch. 

I wont say that you cant sand and polish your top layer of polycrylic, because as soon as i do someone will come forward with a story about their cousins uncles dads brothers son did it one time and it totally worked, as long as you followed this 48 step process during a waning blood moon. What i will say, though, is that the amount of effort and materials youd spend polishing out your top coat, you could go out, buy a rattle can of finish, put on a nice top coat with that and be done with it several times over


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