Black streak in pippy oak

[Rockley]

I've got a black streak, almost like a dye has penetrated the oak throughout the board. Does anyone know what this is? and or how i could cover it up..

See picture below. My current solution is to either trim it off length or width ways (customer wants it removed), personally I'd leave it but I can understand their concern. You can see the cut line on the piece so I have some spare wood to do some trials on. I'd maybe like to try and bleach the wood and then apply a dye to make it oak coloured again, I don't know if that's possible but would appreciate any ideas.

 

[pitch pine]

It is caused by the tannin in the oak reacting with a piece of metal in the timber. Might have been a staple in a hedgerow tree. Not sure whether you can remove the staining.

 

[custard]

You could start messing around with Oxalic Acid, but it's just not worth it. For one thing you'll only affect the fraction of a mill right at the very surface, so the work has to be done on the finished piece or finished component, that makes it too risky if it doesn't work out as by then you've sunk time into it.

At the end of the day it's waste, cut off the stained part and run it through the woodburner.

 

[rafezetter]

You could start messing around with Oxalic Acid, but it's just not worth it. For one thing you'll only affect the fraction of a mill right at the very surface, so the work has to be done on the finished piece or finished component, that makes it too risky if it doesn't work out as by then you've sunk time into it.

At the end of the day it's waste, cut off the stained part and run it through the woodburner.

What about the staining the other side of the cut line? I thought that was what he was asking.

Rockley are you certain that you can't convince the customer that this is part of the natural history of the timber? All timber is different, and this is part of that. I know people prefer "defect free" wood, but then why go for the expense of natural wood at all if you don't accept it for what it is? It might also help to explain to the customer that trying to unify the look will be impossible especially if it's going to have a clear coat; that even should oxalic acid work which is the normal method for such things - there will still be a colour differential, and there will be a time factor to add to the cost of the work.

Removing deep staining from wood isn't like removing a tea stain from a shirt.

If the customer really really wants that stain gone the other possible alternative is a different slab of wood, but that will take time to find, and the added cost.

Basically on the few occasions I've had a "I don't like that defect" from a customer that's going to be complicated to fix I try to point out that all other options, including finding a suitable replacement will cost time and money that will have to be added to the current budget.

I also have no idea how permanent oxalic acid will be in such a situation as the staining goes right through, I've only used it on surface staining - even if it gives acceptable results on the surface can it bleed back from underneath?

 

[custard]

I'd maybe like to try and bleach the wood and then apply a dye to make it oak coloured again, I don't know if that's possible but would appreciate any ideas.

Rather than re-stain back to an Oak colour you could just try a two pack bleach and leave it there. Bleached Oak is currently one of the most fashionable finishes around, here are some library steps and a consol table from a top end workshop that have been finished this way, overcoat with Osmo Raw for some protection without affecting that "driftwood" look.

 

[rafezetter]

Would fuming be an option - it'll go darker, and maybe help unify it a bit?

 

[mrpercysnodgrass]

I would try oxalic acid as a first step. if it does bleach out the stain it should be permanent. Mix up a strong solution of oxalic with boiling water (you will need good thick rubber gloves) using a nylon pad spread the oxalic over the entire board and then with a firm pressure concentrate on the stain for a good five minutes. You may have to make a fresh batch of oxalic to keep it hot but you can also use a hot air gun to keep your solution already on the timber hot. Use the pad to straighten out the solution along the grain and leave overnight. Rinse off with warm water and clean up with rags, repeat two more times.

 

[custard]

When I first started woodworking Oxalic Acid was widely used, for example if Oak components touched sash cramps during a glue up they'd likely stain and so you'd do a spot application of Oxalic Acid to cure the problem. You might wear gloves, I can't ever remember anyone using masks, and you'd work with it right at your bench.

But nowadays Oxalic Acid has fallen out of favour due to the health and safety restrictions that now surround it. One workshop I know stipulates that any use of Oxalic Acid will only be done in the spray shop in front of the extractors while being masked up, and that covers both the initial application and any subsequent sanding of the component. I guess in restoration work you don't have a choice, but for furniture making it's all too much faff. Cheaper to take precautions (like using bearers during glue ups) so the problem doesn't occur in the first place and treat any instances in sawn boards as defects to be cut out and scrapped.

Here's what the data sheets say about Oxalic Acid,

Potential Acute Health Effects:
Very hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Hazardous in case of skin contact (permeator), of eye contact (corrosive). Slightly hazardous in case of skin contact (corrosive). The amount of tissue damage depends on length of contact. Eye contact can result in corneal damage or blindness. Skin contact can produce inflammation and blistering. Inhalation of dust will produce irritation to gastro-intestinal or respiratory tract, characterized by burning, sneezing and coughing. Severe over-exposure can produce lung damage, choking, unconsciousness or death. Inflammation of the eye is characterized by redness, watering, and itching. Skin inflammation is characterized by itching, scaling, reddening, or, occasionally, blistering.
Potential Chronic Health Effects:
CARCINOGENIC EFFECTS: Not available. MUTAGENIC EFFECTS: Not available. TERATOGENIC EFFECTS: Not available. DEVELOPMENTAL TOXICITY: Not available. The substance may be toxic to kidneys, the nervous system, mucous membranes, heart, brain, skin, eyes. Repeated or prolonged exposure to the substance can produce target organs damage. Repeated exposure of the eyes to a low level of dust can produce eye irritation. Repeated skin exposure can produce local skin destruction, or dermatitis. Repeated inhalation of dust can produce varying degree of respiratory irritation or lung damage.

 

[Rockley]

Thanks for quick replies. I'll get hold of some oxalic acid and give that a try I think as I only need to change the appearance of the top surface of the wood. The last 100mm of the piece of oak is to be trimmed off so i can do a tester on that and see what happens. Failing that its time to convince the customer its character and would be a shame to remove it.

I'll keep you all posted.

 

[Lazurus]

Tell him it is the staining from a musket ball embedded many years ago, a bit of provenance always helps!!!!!!

 

[Rockley]

I personally felled this tree in Hastings and had to remove an arrow head from the wood, it seemed to have some eyeball remnants on the end of it....

 

[Rockley]

Tester piece looks really good. The black streaks remaining are epoxy filled cracks. Any thoughts/concerns on finishing over the top of this with osmo oil?

My plan now is to apply some borax to neutralise the acid as I read this was a good idea, then lightly sand and apply the finish.

 

[mrpercysnodgrass]

That looks really good. No need to use borax just plain old tap water will do.