Replies

1. 
   Clay_Williamson | Aug 28, 1999 11:05pm | #1

   *
   Marcella.....oxalic acid is probably the best all around wood bleach..but its extremely dangerous, a pretty potent poison. There are other methods. Start with your stripper. KS - 3 from Klean strip is a pretty good meth/chloride stripper; it's water soluble so clean-up is safe, I like to use automotive thinners to remove the residue and clean the wood after stripping, (Dupont 3602-s) Once your down to your clean bear wood, try sanding out any of the stains/220 grit up to a 400 grit.

   If the stains are still evident then try lime juice, it's an acid also. If no luck try chlorox, it's a good bleach, dilute it to your needs and do some test patterns in small areas first.

   If no luck then go to your oxalic, remember to dilute it 75% w/ water 1st and try test patterns first. Increase the strength as needed to acheive the effect desired.

   A couple of hints :
   Once your bleach/acid has worked dilute the mixture you have used 100% and then wash the entire top to blend your chemical evenly.

   After that wash the entire surface w/ water and then sand w/ 220 and go up to a 500 grit.

   Vacume your surface, wash it with your auto thinner and rotate your rags until nothing shows on your rags.....you should now be ready to stain/seal and finish.

1. 
   Michael_Richwine | Aug 29, 1999 03:51am | #2

   *Here's a slightly different take on Oxalic acid.I refinish / repair / restore a lot of furniture, and Oxalic acid is the first thing I reach for to take out black water stains and weathering. I use other methods too but oxalic takes care of 75% of what I run into.I mix about 3/4 pound of crystals to a gallon of HOT water (3 oz to a quart), and apply it hot -- it works faster. Once the stain is gone, it is usually good to spread the solution around over the surface to prevent spotting or uneven bleaching.Regarding toxicity. You do have to be careful with it, but the primary danger is from the crystals formed when it dries. They are very sharp, and can cause bleeding of lungs and mucous tissues.So, with that in mind, rinse thoroughly with several changes of water. Then let dry thoroughly, and rub with a dark cloth. If there is any residue, rinse again and let dry, until no white residue shows. Then sand and finish normally. By all means, don't sand as long as there is any oxalic residue left -- your nose and throat will tell you that you made a mistake.Michael R.

1. 
   dion | Jul 20, 2012 12:23pm | #3

   Oxalic Acid

   While sanding, I knelt on a large curved panel I constructed out of maple plywood, leaving grey-blue stains on the wood. All I can figure is I must have knelt on my saw table first and transferred some iron residue to the panel. (It was a hot, sweaty day in my shop, and my table saw and outfeel table double as a work surface.) I didn't want to try to sand out the stains and risk cutting through the surface veneer, so I looked up an article on bleaching wood by Jeff Jewitt, which indicated that I should use oxalic acid. I had some lying around that I inherited from my dad, so I mixed some up according to the proportions provided by Mr Richwine and applied it based on his post. It worked like magic! The stains disappeared right before my eyes! Thank goodness, because I did not want to have to build that panel again!

   Thanks, Mr Richwine.

2. 
   HowardAcheson | Jul 22, 2012 07:15pm | #4

   The oxalic bleach I buy has instructions on the label.  Mix 1 pound of oxalic bleach crystals to 1 gallon of hot tap water.  I use smaller quantities so mix 1/4 pound to a quart of hot water.  If you don't have access to a scale, 1/4 pound measures out to 1/2 cup

1. 
   user-64052 | Jul 24, 2012 04:03pm | #5

   it usually does't

   take that much oxalic acid to do it's work. i usuall just take a spoonful to 1/2 -1 cup of warm water. it has to disolve. i use vinegar(acetic acid) to stop the action(neutralize) and then wash with clear water.

   1 lb of crystals will last you many, many years. you are usually just elimminating some tannin/iron black marks and a few drops on it usually does the trip  waste not,want not

   ron

1. 
   HowardAcheson | Jul 25, 2012 11:39am | #6

   You can make any amount you think you need.  Just use the same proportions or whatever proportions called for by the packager.

   I'm a boater and we used a lot to do a 40-60 deck.  I just refinished a two 6 foot x 4 foot cockpit floor gratings.  Took about a quart of mixture to do it.

1. 
   user-64052 | Jul 25, 2012 06:14pm | #7

   I know that Howie

   but most in their small shops will never need over a teaspoon of it at any given time. I sell it out of my shop as it is difficult to obtain around here(in 1 lb increments and most will never use that much in their lifetime.I have perhaps gone through maybe 2 lbs myself in my shop in almost a 40 year span. I also know some that buy it in 25 lb sacks- use it for cleaning up log houses after completion. whatever that you require, but to say to mix up a gallon for most is a little overkill as it will just get poured out somewhere

   ron

1. 
   HowardAcheson | Jul 26, 2012 11:15am | #8

   Re-reading my initial post, I didn't suggest mixing up a gallon.  I just quoted the instructions on the package.  In fact, I went on to say that mixing up a lesser amount was easy.  Just use the same proportions.

   One could even use Barkeeper's Friend which I believe is mostly oxalic acid.  Marine stores will also have some teak cleaner in smaller packages.  Most teak cleaner is mostly oxalic acid.

2. 
   user-64052 | Jul 27, 2012 12:13pm | #9

   guilty

   but for most here a teaspoon would be enough to solve all of their problems with a stain on a small piece of furniture. I more than likely use it at about 20 or 25 -1 and it it needs more I just give it another application.

   I do sell quite a few 1lb containers to the boat people around here and they never come back for more

   ron

2. 
   spiike | Jul 03, 2017 02:09am | #10

   Oxalic Acid

   Hi Howie :) Thank you for your helpful and informative response :)  Much apprecieated. 

   RON @ Sidworks: Jeez fella, get off your high horse! Howies advice was clear and concise, He QUOTED the mixing ratios from the packging, which answered the original question/post, then went on to say that he uses smaller quantities and gives helpful advise on how to do so!

   I found your remarks (Ron @Sidworks) contemptuous and ignorant, You failed to understand his response then continued to behave as though everyone were daft and couldn't work out things for themselves following Howies post and/or their own common sense. and putting links to your stuff in your response was crass and self indulgentand not at all helpful or pertinent to the question.