Oak Stained by Iron

[The Bear]

Hi all

Bit of a follow on from a question I asked last week.
I have had some big oak beams delivered from the mill that have sat on iron tressels. Where they have been in contact the oak has gone black. I understand that there is an acid (or other chemical?) that can be applied to remove the stains.

Anyone know what it is, where to get it and how to go about applying and using it?

Thanks in advance

Mark

 

[johnnyb]

oxalic acid

 

[The Bear]

Thanks Johnny

Do you know where to get it, what strength and how to apply and use?

Mark

 

[JonnyD]

Hi i use a two part bleach that i get from morrells woodfinishes. It is a two part system that is based upon hydrogen peroxide. You have to buy a gallon of each but its quite cheap and works well and is quicker than oxalic acid.

jon

 

[dickm]

It is a two part system that is based upon hydrogen peroxide. You have to buy a gallon of each but its quite cheap and works well and is quicker than oxalic acid.

Buying a gallon of hydrogen peroxide could well result in you receiving a visit by the security services . How do you fancy an orange jumpsuit?

 

[Pekka Huhta]

Oxalic acid removes just the stain, hydrogen peroxide bleaches the whole wood. That's why I prefer oxalic acid, wood starts looking quite pale with peroxide or chloride bleach.

Dissolve as much oxalic acid to warm water as you can. Dilute this with 2-3 parts of fresh water (keep some of the saturated solution undiluted if you need a stronger solution). Apply to stains, let stand for a couple of hours. If there is still some of the stain left, re-apply. If most of the stain is still there, you can use a stronger solution or longer time.

After use, neutralize with baking soda (2-3 tablespoons per 0,5 l water) and rinse the area with warm water.

For more tips just google oxalic acid water stain and you'll get a few thousand different recipes

Pekka

 

[shim20]

scrape it out with a hand scraper

 

[The Bear]

Thanks for the replies

Think I'll try the Oxalic acid route first as I just want to remove the worst staining. These beams are open to the elements so I am happy with some "character" and there are too many to want to bleach everything
Pekka thanks for the practical advice on how to use the acid.

Mark

 

[wcndave]

Long time ago... however:

1. did this work?
2. why do you sometimes get black stains from eg water rings from a glass, is there that much iron in water?

Thanks

Dave

 

[yetloh]

Not my post, but it certailnl does work. I have seen rally bad marking on oak from contact between water based glue and sash cramps during glue up and oxalic acid removed them. In some areas water can gave quite a high iron content so this is certainly a possible cause of the marks you refer to.

Jim

 

[The Bear]

Hi

Yes it did work. I followed Pekkas advice. However this was a rustic outside project, would need some refinement to use for other things.
No idea about the water stains

Mark