Oxalic acid

[hilaryb]

anyone used oxalic acid to cover water stains on wood?

[John Holden]

anyone used oxalic acid to cover water stains on wood?

 

You don't use it to cover stains, you use it to bleach them out.

Use in a very well ventilated area, even outdoors. Protect exposed skin.

[Mike Jordan]

Yes I haven used it with success to remove black water staining from oak which has been allowed to get wet in outdoor use over a period. As previously mentioned it bleaches the timber back to its original colour. If you look at - WWW construction chemicals.co.uk there is a useful demo video of its use and hazards.

Mike.

[WotEver]

If you look at - WWW construction chemicals.co.uk there is a useful demo video of its use and hazards.

Mike.

https://youtu.be/YTHiqtdZMMI

[blackrose]

Yes, I used it to remove stains and clean a teak deck. It worked well.

[Mike Jordan]

You can buy the crystals from the local chemists shop or from eBay My firm rule is to keep it in the original box with the warning signs on. In any other container it looks very much like sugar crystals.

[PeteS]

Anybody tried using rhubarb leaves as they contain oxalic acid?

[Lysander]

Used it on our taffrail with some success, however the black staining which had got deep into the grain of the oak seemed to be beyond the reach of the oxalic acid. The surface stains were much improved.

[Nightwatch]

What about interior bulkheads that are effected by dots of mould? Can you use this on that.

[hilaryb]

thanks.. Obviously needs care. I.e. Gloves and dab with kitchen roll??

[Lysander]

I used a paint brush. Definitely need gloves though.

[John Holden]

Domestic bleach will remove a lot of discolouring and staining but not stains caused by tannin in oak.

[WotEver]

thanks.. Obviously needs care. I.e. Gloves and dab with kitchen roll??

Dabbing won't do it. It needs to be thoroughly wetted.

 

Tony

[AndrewIC]

Oxalic acid is the principal ingredient of Bar Keepers Friend, don't know whether you could use that on wood though!

 

If you use oxalic acid on wood, is it necessary to neutralise it somehow?

Edited February 17, 2016 by AndrewIC

[John Holden]

Oxalic acid is the principal ingredient of Bar Keepers Friend, don't know whether you could use that on wood though!

 

If you use oxalic acid on wood, is it necessary to neutralise it somehow?

 

I doubt if Bar Keepers Friend would have a high enough concentration of oxalic acid to be effective.

 

Use borax to neutralise it.

[bag 'o' bones]

In my wood finishing days we used to use cotton wool to create a poultice around the stain. On vertical surfaces you can create a reservoir with blue tack to hold the poultice in position. Not really suitable larger vertical areas though. Probably best to just replace the panel.

 

Its best to neutralise the oxalic with successive applications of water or else the crystals break through whatever refinish material you apply after (found this out the hard way).