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OK guys and gals, I'm counting on you here! I'm way under the gun with a project I'm doing for a client to be given as a Christmas gift. It's a quartersawn White Oak wine rack (just like the one David Marks did on Woodworks…if you've seen that episode.)

Anyway, I glued up panels 2 days ago with just yellow Titebond. But I screwed up and let my clamping bars touch the wood. No big deal right? Maybe a little glued to scrape right?

WRONG!!!!

The glue or the metal bar or something stained the oak. Here's a pic:

Oak Stain

In this shot, the mark has been scraped down nice and smooth and flush to the wood surface. From what I can tell, the staining occured where the glue or the bit of water I used to clean up the squeeze out contacted the clamp bar and the wood. But there's no discoloration or rusting or anything on the clamp bar. Just a dark stain in the oak…it looks like a burn mark.

Anyone have any ideas to remove the stain? Scraping it didn't help…it seems to be in the wood. My planer's not wide enough to take a few passes at it.

HELP!!!!
 

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Just guessing, Kevin I would assume that you used black iron bar clamps. This look like an iron stain to me. When oak comes in contact with iron in the presence of moisture the tannins in the wood will react with the iron to produce a black stain. Essentially this is one process via which oak can be ebonized.

If you do a search for removing iron stains from oak you will get several suggested remedies. One of the most common suggestions involves using oxalic acid. Here is one that should work. I have used oxalic acid solutions to remove stains on my deck but have never had the problem with oak since I use clamps with aluminum bars.
 

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Discussion Starter · #3 ·
Scott,
I use Bessey k-body clamps. There not black iron pipe, like a pony clamp or sometthing similar, but they probably are carbon steel clamping bars (I'm guessing)
 

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Hey Kevin,
Just what Scott said.
That is a beautiful piece of wood so I imagine you can't hide the stain in an inconspicuous spot The stain is probably a couple of mills deep,and would require some serious scraping and or sanding which might be noticeable on a high gloss finish but not so much on an oil finish. My wife just looked at your picture and said(jokingly) just turn over the board( I had not thought of that). Next time(I know you don't want to hear about next time)slide a piece of any kind of plastic(even paper will work) between the clamp and wood
 

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Discussion Starter · #7 ·
Thanks everyone, and good call on the oxalic acid. Here's what Google found:

Oxalic Acid

Oxalic acid is unique in that it will remove a certain type of stain formed when iron and moisture come into contact with tannic acid in the wood. Some woods like oak, cherry and mahogany naturally contain a high amount of tannic acid and a black stain is formed when the wood gets wet with tap water (tap water contains iron as a trace mineral). A wet glass or leaky vase left on these woods will produce a black ring. Nails and screws will form black rings around the head if the wood gets wet. If tap water is used to wet unfinished oak and mahogany, small gray spots may form on the surface of the wood. Oxalic acid will remove this discoloration without affecting the natural color of the wood.

Oxalic acid is also used to lighten the graying effects of outdoor exposure. It is the ingredient in most deck "brighteners". Used on furniture that has been stripped for re-finishing, it will lighten the color and re-establish an even tone to the wood, particularly oak.

Stain Removal

If you can determine the composition of the stain you can remove it with the correct bleach. Iron based stains are fairly easy to spot. They are grayish-black and usually ring shaped. It may also show up as a splotchy appearance on oak that has been stripped. Before applying the oxalic acid remove the finish first. Mix a saturated solution from dry crystals in hot water and apply to the entire surface, not just the stain. Several applications may be needed with overnight drying in between. Once dry, it's imperative that any residual oxalic acid be removed from the surface of the wood before sanding or finishing. Several rinses with distilled water will remove most of the oxalic acid crystals left on the wood surface. Neutralize the acidic wood surface with a solution made from one quart water with two heaping tablespoons of baking soda.

Thanks again guys…I knew I could count on LJ!!!!
 

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I've had plenty of iron stains from black iron pipe clamps but not any of my K-body clamps. I have both Bessey and Jet, both of which are zinc plated (or chrome?). Thats really weird! I guess I'll have to be more careful as to prevent this from happening.
 
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