# Finishing old oak? joists.



## chaoticbob (1 Oct 2016)

I've stripped the plasterboard from my living room ceiling to reveal the joists above. I'd like to leave them exposed, but at some time in the history of the house the ceiling must have been lath and plaster - there are many nail holes in the joists where the laths would have been attached. The nail holes aren't a problem, but the deep stains around them are - hence the oak? in the subject line. So my questions are: (a) is there any way of bleaching out these stains? and (b) if not, can anyone recommend a stain which might blend in? 
I want to avoid painting the joists black if possible.
Rob.


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## adidat (1 Oct 2016)

An angle grinder with a 40 grit sanding disc will remove dirt, grime and staining pretty quickly, then oil them. If you want a less rustic look then go over them with some 180 grit then oil. Just be prepared for a lot of dust when using the grinder!

Adidat


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## chaoticbob (1 Oct 2016)

Thanks for the reply adidat - I'd assumed that the staining around the nail holes was because of the reaction between the iron nails and tannin in the wood, so would extend to the depth of the holes. But maybe it doesn't work like that?
Robin


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## Phil Pascoe (1 Oct 2016)

Oak? they might not be oak, it might be that the original laths were chestnut, which would provide the tannin for the stain. Chestnut was commonly used as it cleaves easily and is rot resistant, so was ideal for fairly long, straight (and small section) lengths. If this is the case the staining might be be quite shallow.


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## chaoticbob (1 Oct 2016)

Thanks Phil, I'd never have thought of that possibilty. I'll take a sander/angle grinder to it and see what happens.
Robin.


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## rafezetter (2 Oct 2016)

Well if you wanted to remove them or reduce to some extent - oxalic acid fairly strong will help 1:1 ratio with water. Comes in a powder. Alternatively, if you were thinking you might be OK with the dark look you could try the old "steel wool in vinegar" to darken them to blend in the stains without having to paint them black (cue Rolling Stones), if the wood doesn't have enough tannin to go as dark as you'd like, alternate the vinegar solution with ridiculously strong mix of coffee, and do it just as they are getting to the "damp" stage - use 2 different brushes with a rinse in between applications or the reaction will occur on the brush, not the wood.

You can get very subtle shades that way and still leave grain visible. There are ofc commercial ebonising stains but they aren't quite as controllable with shades as the homebrew.


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## chaoticbob (3 Oct 2016)

rafezetter":1vyjn9tj said:


> Well if you wanted to remove them or reduce to some extent - oxalic acid fairly strong will help 1:1 ratio with water. Comes in a powder. Alternatively, if you were thinking you might be OK with the dark look you could try the old "steel wool in vinegar" to darken them to blend in the stains without having to paint them black (cue Rolling Stones), if the wood doesn't have enough tannin to go as dark as you'd like, alternate the vinegar solution with ridiculously strong mix of coffee, and do it just as they are getting to the "damp" stage - use 2 different brushes with a rinse in between applications or the reaction will occur on the brush, not the wood.
> 
> You can get very subtle shades that way and still leave grain visible. There are ofc commercial ebonising stains but they aren't quite as controllable with shades as the homebrew.



Thanks, precisely the kind of info I was after. This opens up a field for experimentation - presumably almost any iron salt, not just the acetate would do. My first thought was to try the oxalate treatment to lighten the existing stain, then iron (and coffee if necessary) to match on the rest, but maybe that won't work because any excess oxalic acid will mop up the iron ions. I need to make some experiments. Maybe I can write the expresso machine I've been wanting to the 'home improvement' budget on the back of this  
Thanks again, Robin


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## rafezetter (4 Oct 2016)

chaoticbob":3bwy807u said:


> Thanks, precisely the kind of info I was after. This opens up a field for experimentation - presumably almost any iron salt, not just the acetate would do. My first thought was to try the oxalate treatment to lighten the existing stain, then iron (and coffee if necessary) to match on the rest, but maybe that won't work because any excess oxalic acid will mop up the iron ions. I need to make some experiments. Maybe I can write the expresso machine I've been wanting to the 'home improvement' budget on the back of this
> Thanks again, Robin



I would imagine any solution with a good level of iron would do the job, but this can also be varied according to dilution with water.

I don't think the oxalic acid once applied and dried will have much of an effect on anything put after, even though it'll remain in the wood the acidic solution you use won't conflict with it. However just to be cautious and because you make up what's little more than a sloppy paste just dab it with a small brush where you need it - the reaction is pretty quick, so it'll still be wet when it's done it's thing so a paper towel can remove the rest of the excess.

Well espresso would be the right sort of strength - when I'm doing this I heap maybe 4 or 5 dessert spoons of proper (but cheap) coffee grounds into a jar with hot water and let it steep, then only decant a bit as I need - and remember to NEVER return any unused mix that's been near the iron solution or you'll nix the whole batch.

I wouldn't worry too much about getting a perfect match anyway - part of the history of the wood if some of the nail stains are visible under scrutiny, which won't be that often anyway in reality; remember some people pay good money to fake that!


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## ED65 (4 Oct 2016)

chaoticbob":2c386b1o said:


> This opens up a field for experimentation - presumably almost any iron salt, not just the acetate would do.


I don't know if any iron salt will do but some others definitely will. In the past this was done with other iron compounds and not commonly with iron acetate because the former were commonly available in powder form. 

Tea works better than coffee to introduce tannins by the way. "Oak tea" made with fallen oak leaves, bark and definitely if you can find any, oak galls break them up with a hammer before steeping).


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## ED65 (4 Oct 2016)

rafezetter":1bznrai4 said:


> I don't think the oxalic acid once applied and dried will have much of an effect on anything put after


It will if it any remaining is unreacted.

Oxalic acid is supposed to be very thoroughly removed from treated wood anyway, with at least two rinsings using fresh water each time. This is for safety reasons apart from anything, oxalic acid is quite poisonous.


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## andersonec (4 Oct 2016)

Iron or steel and Oak do not mix, just try putting a bit of steel onto a damp piece of oak and leave it for half an hour, that's why there are black marks around the nail holes. The Oxalic acid may tone them down a tad but if all else fails try staining them with a dark Oak stain.

Andy


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## chaoticbob (9 Oct 2016)

Thanks for further replies. I now have a tub of oxalic acid, and a bag of ferrous sulphate is on its way. I'm not too worried about the toxicity of the acid - if any very tall person starts chewing on my my joists though I'll try to stop them :wink: 
I need to experiment and will report back - in the meantime (I know you guys like pics) this is where I am at the moment:







Rob


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## chaoticbob (5 Nov 2016)

Well, I've been doing some other stuff, so my wife has taken over this task - she's sanded down two joists (thirteen more to go) with a delta sander, but she's finding it hard going. So she had a look on t'interweb and decided she needs a Festdrool Rotex. I'm going to set her on cutting M&T's for her next job. 
The oxalic acid treatment worked to some extent, but the nail stains are just too old and deep to bleach out, so we're going for blending. For staining do you just bung the the wire wool in the vinegar, let it fizz a bit and then paint on the solution onto the oak?
Rob


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## ED65 (7 Nov 2016)

chaoticbob":3aj2nhil said:


> For staining do you just bung the the wire wool in the vinegar, let it fizz a bit and then paint on the solution onto the oak?


No, although some guides do suggest that's all that's necessary they're way off. You should leave the steel wool to react for a good long while, at least a day or two but actually the best guides tell you to leave it until it has nearly dissolved the steel which is good advice as it guarantees you have the strongest solution. This can always be diluted with water if it's found to be too strong (rarely a problem!) oh and you'll probably need to sift it to remove some floating rust particles.

Once you have your solution then you do just paint it on the wood with a brush. On oak the reaction should be very fast, it should turn grey within a few moments but leave it to dry before assessing if you need to go further. You can apply the liquid multiple times, allowing each to dry, to get the wood darker and greyer. At best oak will turn sort of charcoal grey which when you apply finish gives you a good black, comme ça:


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## chaoticbob (7 Nov 2016)

Many thanks for your detailed advice ED65. Most helpful. I'll post before/after pics in due course - if it turns out OK!
Rob.


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## RogerS (8 Nov 2016)

We simply left our joists as they were after removing the lath and plaster. Those marks - they are part of the heritage of the house. Anyway, how many times does one actually look up at the ceiling ? 

And please, please don't oil them.


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## ED65 (8 Nov 2016)

Why no oil Roger?


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## custard (8 Nov 2016)

chaoticbob":2aewuggx said:


> The oxalic acid treatment worked to some extent, but the nail stains are just too old and deep to bleach out, so we're going for blending. For staining do you just bung the the wire wool in the vinegar, let it fizz a bit and then paint on the solution onto the oak?
> Rob



Rob, here's the thing about iron staining Oak. 

The wire wool/white vinegar is the _easy_ bit, you can be pretty cavalier about that part of the process and still get an adequate result. White vinegar, apple vinegar, dilute acetic acid, a handful of wire wool, a healthy pinch of iron filings, 48 hours, three weeks; none of that makes much difference.

The trickier part is the tannin side of the equation. The fact is that even with Oak or Sweet Chestnut, surface tannin levels are _extremely_ variable. You might get lucky (for example freshly cleft, recently felled oak) and you'll go straight to jet black with no additional tannin. But kiln dried Oak where the surface has been prepared then had a few weeks to oxidise, well you can lather on the steel wool/white vinegar all you like however you'll probably get no more than a patchy mess with a bit of a purple cast rather than black. Your oak will fall somewhere on this spectrum. 

So to be safe you need to prime the surface with plenty of fresh tannin. The best solutions are made from Oak galls, I collect them in the forest when walking the dogs, grind up a handful of these and you'll get the deepest black and also the deepest concentration. Next most effective is big handful of fresh Oak shavings and Oak bark boiled up. If you don't have access to either of these then super strong tea will do the job, but you won't quite get the colour and penetration you will with the other methods. You'll get close, but just not quite as good. Whatever you choose, an important step is to add one drop of washing up liquid as a surfactant that will break the surface tension and get the solution deep into the pores of the timber. This makes a tremendous difference, but I've never seen it referenced on any of the often dodgy formula you'll find on the web.

These are what Oak Galls look like, given that people used to make black ink with these rather than choosing Oak bark or Oak shavings you can safely conclude they genuinely bring something extra to the process.






So, don't worry too much about the iron solution, it's the _tannin_ that'll trip you up.

One final thing, if you end up with a purple/mullberry colour you can make it blacker with burnishing or brushing with a stiff bristled brush (not steel bristles or you'll tear out the softer grain), and if that doesn't work enough then oiling or waxing will move the colour still further towards black.

Before embarking on joists you really should practise with some scraps of Oak at your bench, you might conclude it's all too much of a faff to repeat the process perched on top of a step ladder. If so, better to find that out earlier rather than later.

Good luck!


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## RogerS (8 Nov 2016)

ED65":uyqm7zlp said:


> Why no oil Roger?



Why oil them? People in the past never did?


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## ED65 (9 Nov 2016)

@RogerS I'm not sure that's so Roger but why should we care? Oiling makes the wood look better ('specially after staining with iron acetate) which is reason enough to do it if you want, aside from the bit of surface protection it adds.

@chaoticbob Re. adding tannin solution to the wood if necessary, don't worry if you've already added a coat of the vinegar solution. The two things can be applied in either order to the same effect.


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## RogerS (10 Nov 2016)

ED65":ukpik5v5 said:


> ..Oiling makes the wood look better ....



It doesn't. YMMV


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## ED65 (11 Nov 2016)

I know tastes vary Roger but I'm struggling to understand why someone would prefer a matt grey to a rich black ;-)


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## RogerS (11 Nov 2016)

ED65":2mvs5h4i said:


> I know tastes vary Roger but I'm struggling to understand why someone would prefer a matt grey to a rich black ;-)



It was the Victorians who started painting beams black. Before then they were left to age naturally.


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## ED65 (11 Nov 2016)

I think you're missing the point here Roger, chaoticbob is going ahead with treating the oak with an iron acetate solution which means the wood will be a dull grey unless some finish is applied to 'wet' the surface.


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## custard (11 Nov 2016)

ED65":n37322bf said:


> chaoticbob is going ahead with treating the oak with an iron acetate solution



I hope for his sake he doesn't! It's an entirely impractical technique for dealing with a large expanse of heavily fissured, overhead woodwork. 

Here's a Bubinga desk with iron stained Oak legs that I delivered a couple of weeks ago, I do quite a lot of this stuff so I know what I'm talking about when I say I'd really hate to be perched up on a ladder making multiple applications of heavily staining chemicals which are dripping down on both me and the floor!


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