# Black stains after stripping oak table - any suggestions?



## TCR (20 Oct 2021)

I have been stripping a 50 year old oak table - See the photos.

30 years ago it was re-varnished with very dark black polyurathane varnish.

I stripped with water based varnish stripper which I have used lots of time before. The top has stripped really well, but the legs (all 6 of them!) have a residual dark staining which you can see in the photos.

Any ideas as to how to get rid of these stains before re-finishing?

- sanding isn't practical because the legs are round and it would probably take forever by hand.

- I tried Wood Bleach but hasn't touched them.

- Could it be tannin - I will try Oxalic Acid crystals- but is it likely to be tannin?

Also, the dark patches look much worse when the legs are wet (as you can see in one of the legs which is still wet from the re-applied wood bleach), so I am assuming when we re-finish the table they will be dark too when the oil or varnish is applied. 

We want a rich but light oak finish but nothing like the dark brown/black it was before - any suggestions on what finish to use?

The legs are a pain, because the top is stripping really well.

Thanks, Tim


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## gog64 (20 Oct 2021)

More experienced people will be along soon, but in the meantime my 2p worth. That doesn’t look like tannin staining to me. It looks like the dye in the varnish has leached through the wood underneath. FYIW I think it looks great! I’ve been working with some “exotic” woods recently (not my usual thing) and it looks very similar to a very expensive wood I’ve been turning! If I’m right, now that the dye is exposed to UV you should see it fade fairly quickly. 12 month in a sunny spot might sort it out


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## kinverkid (20 Oct 2021)

I'm with gog64. I think it's the dye too. I'm going to watch this post because I'm interested in if or how this can be remedied too.


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## baldkev (20 Oct 2021)

I agree with the dye comments.... 
If it were bacteria in the grain or weathering it could be taken out using oxalic acid. You could try that, but if its dye, which i agree it most likely is, oxalic will have no effect. The other thing which can work to revive timber colour is hydrogen peroxide.... you can buy 9% peroxide in boots etc very cheaply. Again, i wouldn't expect any difference with this


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## baldkev (20 Oct 2021)

Actually..... just thinking..... as said above, it does look cool, so how about doing a test on an inconspicuous area? I would get a couple of the osmo oil tester packets, maybe white tint and honey tint.... you might be amazed how it comes up


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## Argus (20 Oct 2021)

A while back the reverse effect picked out in white - 'Limed Oak' - was all the rage.

We don't seem to see a lot of it about now........


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## TCR (20 Oct 2021)

baldkev said:


> I agree with the dye comments....
> If it were bacteria in the grain or weathering it could be taken out using oxalic acid. You could try that, but if its dye, which i agree it most likely is, oxalic will have no effect. The other thing which can work to revive timber colour is hydrogen peroxide.... you can buy 9% peroxide in boots etc very cheaply. Again, i wouldn't expect any difference with this


Thanks for the reply. baldkev. I have ordered some of the Oxalic acic crystals and will give it a try. In the meantime I have some 9% hydrogen peroxide and I will try that too.


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## TCR (20 Oct 2021)

gog64 said:


> More experienced people will be along soon, but in the meantime my 2p worth. That doesn’t look like tannin staining to me. It looks like the dye in the varnish has leached through the wood underneath. FYIW I think it looks great! I’ve been working with some “exotic” woods recently (not my usual thing) and it looks very similar to a very expensive wood I’ve been turning! If I’m right, now that the dye is exposed to UV you should see it fade fairly quickly. 12 month in a sunny spot might sort it out


Thanks gog64, sadly we are aiming for the legs to look like the top so embracing the dark patches would be a very last resort. My gut feeling is that it is the dye but I will try the oxalic acid and also hydrogen peroxide and see what happens. 12 months in a sunny spot would be wishful thinking with the UK weather!


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## baldkev (20 Oct 2021)

Ok, oxalic needs warm to hot water for the best results. Leave it 10 mins and then rinse or wipe with fresh water to neutralise the acid. Best to wipe peroxide with water too, probably a similar 10 minute gap


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## TCR (20 Oct 2021)

baldkev said:


> Ok, oxalic needs warm to hot water for the best results. Leave it 10 mins and then rinse or wipe with fresh water to neutralise the acid. Best to wipe peroxide with water too, probably a similar 10 minute gap


Great advice re. the hot water, thanks. Do you know a good ratio for crystals to water? I have heard 8 to 1, does that sound about right?


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## baldkev (21 Oct 2021)

I usually put a heaped tablespoon to anout 200mm


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## the great waldo (21 Oct 2021)

The legs are beech. oxalic acid or rustins 2 part bleach should do the trick. You might have to do it a few times.
Cheers
Andrew


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## Illy (21 Oct 2021)

I stripped a similar table. When I removed the legs the original mounting holes from the lathe were still there, so I was able to put them straight back on the lathe and re-sand whilst maintaining the original shape. Quite a quick process too.


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## TCR (21 Oct 2021)

the great waldo said:


> The legs are beech. oxalic acid or rustins 2 part bleach should do the trick. You might have to do it a few times.
> Cheers
> Andrew


Hi James, Thank you, I was thinking that the legs might not have been oak but another wood. Especially because the top and the stretchers cleaned up so perfectly. I will try the Oxalic acid when it arrives and if that doesn't work then I'll Have a go with the Rustins, that said, the Liberon wood bleach didn't touch it. Thanks again.


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## TCR (21 Oct 2021)

Illy said:


> I stripped a similar table. When I removed the legs the original mounting holes from the lathe were still there, so I was able to put them straight back on the lathe and re-sand whilst maintaining the original shape. Quite a quick process too.


Sounds a perfect solution, but sadly I don't have a lathe.


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## TCR (21 Oct 2021)

james the restorer said:


> Hi
> When I strip pieces, I usually wipe over the entire piece with Liberon wax and polish remover
> 
> 
> ...


Thanks for the tip. I may try this if the Oxalic acid doesn't work.


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## Jacob (21 Oct 2021)

I'm lazy so I would just go with finish to match with least trouble. An off the peg "oak" stain? Or just leave it as is? Paint? etc


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## Sgian Dubh (21 Oct 2021)

TCR said:


> I stripped with water based varnish stripper which I have used lots of time before. The top has stripped really well, but the legs (all 6 of them!) have a residual dark staining which you can see in the photos.
> 
> Any ideas as to how to get rid of these stains before re-finishing?
> 
> ...


As the great waldo pointed out the table is made of two different materials; the top is coarse textured ring porous oak and the underframe is fine textured diffuse porous beech. There are remnants of the old pigmented varnish lodged in the pores of both wood species. In the oak it is mostly apparent lodged in the distinct dark bands of the coarser and more open spring growth. In the case of the beech which has a fine grain lacking a marked distinction between spring and summer growth density and texture the remaining pigmented finish is relatively evenly spread throughout the small pores of the timber's surface.

I suspect the bleaching options suggested by others, whether you use A+B bleach or oxalic acid, or both, won't remove the black colour from both the wood species. If either or both of the bleaches work then you could follow up with a dye of your choice and refinish with varnish or similar. If, on the other hand, the bleaching strategies don't work you might consider applying different finishes to the different parts. You could, for example, paint or dye/stain plus polish the underframe one colour and finish the oak top just with a clear finish, such as an oil varnish which itself will darken the oak, but leave the dark pigmented bands of coarse spring growth.

I don't think you'll ever be able to get the underframe to closely match texturally the appearance of the oak because the two wood species have different texture (coarse and smooth or fine), but you should be able to get a close colour match by finishing both with a dark stain or dye plus polish. However, that is the look you've just removed and you want to get away from that, so maybe the two different treatments for the two wood species you're dealing with might be worth considering. Slainte.


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## baldkev (21 Oct 2021)

I found, when looking, most 'wood bleaches' included the peroxide. I tested 2 kits, both were 'a and b' kits. Painting on a and then b helped a bit but notbenough, so i did patches if just a, then just b and ultimately i found that the peroxide portion worked as well on its own as with the second chemical ( i forget what it was ) so i bought a bottle of peroxide for a few quid and tested that against the a and b..... no discernable difference!! Well about 15 quid difference in price


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## the great waldo (21 Oct 2021)

Hi Tim
Tonally the sanded top doesn't look too far off the shade of the legs. I would first wet down the wood with some meths, and see how the shades match up. Then use some thing like a spirit based golden oak for the whole lot and then use a slightly darker shade of oak to blend the shades till legs and top match. By the way oxalic acid is pretty good for clearing dark stains unless the stains are pigmneted. You could try using a small brass wire wheel thingy in a dremel which should get you into the corners without too much damage. Try staining light at first ( you can always go darker) I think with a little colour the dark bits won't be so obvious and you may get a nice effect. Try and make sure the stains are light fast Morrells alcohol stains used to be really good (at least 30 + years ago when I used to buy from them!)
Cheers
Andrew


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## TCR (22 Oct 2021)

Sgian Dubh said:


> As the great waldo pointed out the table is made of two different materials; the top is coarse textured ring porous oak and the underframe is fine textured diffuse porous beech. There are remnants of the old pigmented varnish lodged in the pores of both wood species. In the oak it is mostly apparent lodged in the distinct dark bands of the coarser and more open spring growth. In the case of the beech which has a fine grain lacking a marked distinction between spring and summer growth density and texture the remaining pigmented finish is relatively evenly spread throughout the small pores of the timber's surface.
> 
> I suspect the bleaching options suggested by others, whether you use A+B bleach or oxalic acid, or both, won't remove the black colour from both the wood species. If either or both of the bleaches work then you could follow up with a dye of your choice and refinish with varnish or similar. If, on the other hand, the bleaching strategies don't work you might consider applying different finishes to the different parts. You could, for example, paint or dye/stain plus polish the underframe one colour and finish the oak top just with a clear finish, such as an oil varnish which itself will darken the oak, but leave the dark pigmented bands of coarse spring growth.
> 
> I don't think you'll ever be able to get the underframe to closely match texturally the appearance of the oak because the two wood species have different texture (coarse and smooth or fine), but you should be able to get a close colour match by finishing both with a dark stain or dye plus polish. However, that is the look you've just removed and you want to get away from that, so maybe the two different treatments for the two wood species you're dealing with might be worth considering. Slainte.


Wow, thanks for the extra detail on the various grains and the advise on possible alternatives. e.g. the legs being different colour from the base. This is a last resort but might end up the pragmatic solution. We like the darker grain detail on the top so that won't be a problem - it is the legs that just look patchy. Anyway, let's see how the Oxalic acid works. The whole purpose of the exercise is to get away from the dark finish, hence striving to solve the problem rather than cover it up. Thanks again for the level of detail, much appreciated.


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## TCR (22 Oct 2021)

the great waldo said:


> Hi Tim
> Tonally the sanded top doesn't look too far off the shade of the legs. I would first wet down the wood with some meths, and see how the shades match up. Then use some thing like a spirit based golden oak for the whole lot and then use a slightly darker shade of oak to blend the shades till legs and top match. By the way oxalic acid is pretty good for clearing dark stains unless the stains are pigmneted. You could try using a small brass wire wheel thingy in a dremel which should get you into the corners without too much damage. Try staining light at first ( you can always go darker) I think with a little colour the dark bits won't be so obvious and you may get a nice effect. Try and make sure the stains are light fast Morrells alcohol stains used to be really good (at least 30 + years ago when I used to buy from them!)
> Cheers
> Andrew


Thanks for the info on the stains. The "finishing" was due to be phase two, but as you point out, the new staining could end up solving the problem with the old residue.


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## TCR (22 Oct 2021)

Sgian Dubh said:


> As the great waldo pointed out the table is made of two different materials; the top is coarse textured ring porous oak and the underframe is fine textured diffuse porous beech. There are remnants of the old pigmented varnish lodged in the pores of both wood species. In the oak it is mostly apparent lodged in the distinct dark bands of the coarser and more open spring growth. In the case of the beech which has a fine grain lacking a marked distinction between spring and summer growth density and texture the remaining pigmented finish is relatively evenly spread throughout the small pores of the timber's surface.
> 
> I suspect the bleaching options suggested by others, whether you use A+B bleach or oxalic acid, or both, won't remove the black colour from both the wood species. If either or both of the bleaches work then you could follow up with a dye of your choice and refinish with varnish or similar. If, on the other hand, the bleaching strategies don't work you might consider applying different finishes to the different parts. You could, for example, paint or dye/stain plus polish the underframe one colour and finish the oak top just with a clear finish, such as an oil varnish which itself will darken the oak, but leave the dark pigmented bands of coarse spring growth.
> 
> I don't think you'll ever be able to get the underframe to closely match texturally the appearance of the oak because the two wood species have different texture (coarse and smooth or fine), but you should be able to get a close colour match by finishing both with a dark stain or dye plus polish. However, that is the look you've just removed and you want to get away from that, so maybe the two different treatments for the two wood species you're dealing with might be worth considering. Slainte.


Thanks Sgian, you make excellent points. Much appreciated.


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## TCR (24 Nov 2021)

Update on finished table legs with black dye residue stains. Thanks again for all those who made suggestions. As many suggested, the problem was a bit of a lost cause and the bottom line was, the stains could not practically be shifted. I tried: Oxalic Acid, Wood Bleach, Hydrogen Peroxide, White Vinegar, Lots and lots of elbow grease with 80 grit. In the end we took the pragmatic approach and stopped trying to remove and instead, live with the results. Finished the bare wood with Rustins Medium Oak wood dye followed by a coat of Ronseal matt water based varnish, then a coat of Wickes Walnut water based varnish, quick rubdown with 600 wet and dry and then finished with a final coat of the Ronseal clear matt varnish. I went for the 2 clear and one walnut because I didn't want to get too dark. We were VERY happy with the top of the table and the legs with the various finishes looked passable and match the chairs very well. Photos attached. Now onto the next project - restoring an old Pixiphone xylophone !


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## the great waldo (24 Nov 2021)

Hi Tim
You've done a great job on that. The warm colour on the top is really good. Just watch out for sloshing red wine on it as it goes really deep into oak (don't ask me how I know)

Cheers
Andrew


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