Oxalic Acid - Bleaching water stained oak.

Oxalic Acid - Bleaching water stained oak.

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dhutch

Original Poster:

15,246 posts

204 months

Wednesday 2nd October
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Has anyone used Oxalic Acid on a wooden floor and can help with practical advise on a good outcome?

We have a similar stain on an oak floor, 1/4" thick oak tiles nailed on floorboards, which has got damp in a few area, mainly around the outside door before we moved in and after 6 years of covering it up with a large turtle matt its time to think about refinishing the floor.

Looking online it appears to can no longer buy the crystals over the counter, but you can get premixed solution up to 10% and it appears that 5-10% solution will work fine, with some guides recommend a saturated solution at 60 grams per litre water, which is only 6% by weight anyway.

Looks like I can get 2.5l of 10% for £16 so that all seams reasonable?
https://www.ebay.co.uk/itm/355968515203?

Removed the finish, paint it on, let it dry, rinse it down with water and or bicarb.
Stand back to admire much stain reduction, refinish to suit....? oh, and wear gloves!

Any other hits and tips?





julianm

1,590 posts

208 months

Wednesday 2nd October
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What a shame! I'd try an old style cabinet scraper or Skarsten type to get the finish off & hopefully the worst of the blackening. Try a tiny corner first to see how it goes.
I'm sure you know oxalic is very toxic so keep it safely away from kids.
Good luck & post new pics!

gazlar53

57 posts

84 months

Wednesday 2nd October
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https://www.constructionchemicalslimited.co.uk/en/...

Bought from here before but not practically used it myself.

AndyTR

549 posts

131 months

Wednesday 2nd October
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I'd be tempted to speak to a French polisher and see if they can sort that properly.

Aston Traveller

397 posts

155 months

Wednesday 2nd October
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My other half used oxalic acid crystals when you used to be able to buy them. I warned him that it went through skin so don’t get it on you. Of course he got his jeans soaked and ended up in bed for 2 days.
Moral of the story is - yes wear gloves but also don’t get it on any other part of your skin as it will be absorbed.

harrycovert

452 posts

183 months

Wednesday 2nd October
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When I used on antique furniture I used crystals and used it hot don't put in a ferrous container to heat it

OutInTheShed

9,323 posts

33 months

Wednesday 2nd October
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I've used it on boats, with varying degrees of success.
You can also get peroxide based wood bleach.

I tend to brush it on, keep scrubbing it for a while with an old toothbrush then leave it to soak for a bit.
Rinse, neutralsie, rinse again
Dry with hot air gun

You could also consider removing the worst bits of wood and replacing with new.

AlvinSultana

885 posts

156 months

Wednesday 2nd October
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I have used it on green oak that had been stained during construction and it certainly did the job.

Nasty stuff as others have pointed out.

However looking at your pictures I would be tempted to hire a floor sander for a weekend (£50), and buy a couple of litres of Tung oil and some white spirit.

The finish will be stunning and well worth the effort.

(caveat being that the whole of the floor is decent enough to refinish)

dhutch

Original Poster:

15,246 posts

204 months

Wednesday 2nd October
quotequote all
Yeah, lots of options and good suggestions.

I have a sharp carbide scraper and and fairly confident I can remove the finish fairly easily.

The other room has had 1-2mm sanded off with an industrial floor sander by the previous owners and it does look nice, finished in clear water based sealer to a much lighter shade, and that is always an option but my plan at this stage is a good wash and a light hand sand to remove any loose material and refinish. We have young children and two dogs, so it's going to be an 80-20 job for now, which also leaves plenty of wood should someone want to sand it back hard in the future.

Noted about it being nasty stuff, I'm not the best at heading warnings, so a good reminder this is not one to skimp on!

dhutch

Original Poster:

15,246 posts

204 months

Thursday 3rd October
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Forgot to take any last night, but I'll get some photos of the rest of the floor, as well as the other room tonight.