Plaster stains on composite deck?

Posting for a friend from the WCR forum who was too chicken. I thought it was an interesting question, though…

“I have a composite deck that has plaster stains and I’m stumped as to how to clean it. I tried the turbo nozzle and a 2% SH mix.
No luck, once the deck dried the stain was still there.

I’m stumped and I’m too intimidated as a noob to go post that in PWR as my first post.”

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My thinking is he might need some type of acidic cleaner to get it out. Maybe OneRestore.

I’m a bit surprised that water and SH didn’t take it up, though. Didn’t know plaster could be that stubborn.

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@EaCoChem and Prosoco both offer mortar removal products, don’t know if they’d be safe to use on composite deck. Might not be any worse than a turbo nozzle lol.

I once used EBC on brick to remove a grout slurry spill from a contractor washing his equipment nearby. I didn’t have any acids with me that day and was quite surprised it took it off.

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According to Google, acid should remove it. If that’s a first gen Trex deck I’d apply oxalic to the whole deck with some surfactant and scrub the stained areas then rinse after a few minutes. If that doesn’t do it, do some tests with stronger acids. Just a suggestion as I’ve never actually done this before.

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I’d try vinegar first and then move up the acid ladder if that doesn’t take care of it. Vinegar is really good with gypsum and calcium- based plasters, which that stain looks to be. Long soak and then adequate pressure


Not a question you see everyday. Could be OneRestore, NMD-80 or maybe even HD Britenol. if i were to test and had any of these products id probably test NMD-80 first.

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Ended up being paint not plaster.

But you had to be on the WC forum to get that info. lol

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I have the exact same problem now. We rented out our airbnb home for the weekend and we got these paint stains now.

I’m thinking someone used some sort of shoe spray paint or something? Idk but does anyone have experience removing these white paint stains.