stain on old oak table

My father-in-law gave us an old round oak dinner table that his brother had given him several years before. He said that it had originally been painted white and a couple years ago he stripped off the paint, sanded it, and put a coat of clear varnish on it. The wood looks great but there's a very annoying 3" stain in the middle of the table. We don't know what the stain is from, it's a darkish red color that's a bit darker in the middle than at the edges. My father-in-law said he tried sanding it out but had no luck. Fortunately I don't think he sanded very much.
I've read on here about using oxalic acid for some types of stains and wonder if I should try it on this one? Of course I'll have to strip the varnish off first, but since we want to use this table in our home we have to get rid of that stain first. Will oxalic acid work on a variety of unknown stains like this one? Any advice would be appreicated.
Thanks, David
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Probably will. Oak is known for dark stains from metallic traces dissolved in water. Oxalic acid is packaged as wood bleach but chech label as there are other bleaches also. Paint store usually has. Believe www.homesteadfinishing.com has article about bleaching.
On 26 Jul 2004 22:27:36 -0700, snipped-for-privacy@bellsouth.net (David) wrote:

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I just read an article on using bleaches to remove stains and realize that maybe it would be wiser to use a strong concentrate of pool chlorine on the stain. Would I put the bleach on just the stain, or over the whole top of the table? Still hoping for any other advice.....thanks.
David
snipped-for-privacy@bellsouth.net (David) wrote in message

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I just read an article on using bleaches to remove stains and realize that maybe it would be wiser to use a strong concentrate of pool chlorine on the stain. Would I put the bleach on just the stain, or over the whole top of the table? Still hoping for any other advice.....thanks.
David
snipped-for-privacy@bellsouth.net (David) wrote in message

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no. bleach is basic. oxalic acid is, well, acid.
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I'm not sure which question your "no" is referring to? Should I try oxalic acid or a strong pool chlorine for this specific stain? Apply only to the stain or the whole table top? Again, I appreciate your help.
David
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Oxalic acid is a bleach. Hypochlorous acid is "chlorine bleach," created by dissolving sodium hypochlorite in water.
Use the oxalic, or maybe those peroxide types. It's oxidation that bleaches.

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Whether alkaline or acid, each bleach will leave a residue even if all the oxidative power is uused up. Wood fibers would remain susceptible to acid or alkaline hydrolysis. So, after using bleach, use PLENTY of water to rinse away the residue, then use the same quantity of water again.
--
Best regards
Han
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If I understand you correctly, the stain is below a finish of varnish. You will have to remove the varnish to get to the stain. The stain should have been dealt with before finishing.
As nospambob pointed out, you will need oxalic acid. It is not a bleach in the same way that chlorine or peroxide is. It works on a very particular type of stain that is very common on oak or other high tannin woods.
Good Luck.

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Yep, and as this is a red, rather than black, it doesn't seem to need the Fe+++-eating stuff.
That's where oxalic excels. Ferric tannate / ferrous tannate.

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Would most paint stores have oxalic acid? Or where might I find it?

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Yep, they would. Neat thing is, you can try some of the peroxide underneath the table to make sure it doesn't to anything untoward, then on the red. Almost bet there's some downstairs named oxy(whatever). If no joy, purchase oxalic acid of little other use than the purpose for which you intend.

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Sorry, but I just don't understand....obviously because I'm new to this.... Are you saying I *should* use the oxalic acid for the dark red stain on this oak table or something else? And, whatever I use, should I treat the whole table table top or just the stain? Please be as specific as possible ok?
Thanks, David

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FIRST try what's probably easily available - the oxy stuff. The oxalic acid is used against iron stain, which you don't seem to have, and can be purchased if the other doesn't work.
As with anything you do, experiment underneath and out of sight to determine side-effects prior to the actual thing.

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So this reddish 3" stain is probably a natural occurance in oak? I thought it looked like something dark red that was spilled there many years ago and no one could get it off. If the stain were to be some kind of drink or food would I still use the oxalic acid?

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Oxalic acid is used to remove the dark stains caused by iron reacting with the tannins in the wood. If you have any other kind of stain, it won't help you.

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