Questions About Oxalic Acid

[terrymac]

Have a couple of question for those of you that use oxalic acid prior to dying or antiquing. How much do you apply to the leather, ie, how wet do you get your leather? My comcern would be any affect on your tool burnishing if you used too much. Also, what are you using to apply to the leather? Any help would be greatly appreciated

Terry

[Randy Cornelius]

For just general cleaning I use about a 1/2 tsp in quart of water. I will apply with a sponge to the intire piece of leather. After it is cleaned to my satisfaction I go back over it with clean water with a sponge. Let it stand for several minutes to see if it is cleaned to your satisfaction, if not repeat process. Don't leave your sponge setting in the solution very long. will break down sponge. For spot cleaning apply to the area and then go over the intire piece with clean water. Make sure it don't change the color or lighten the leather in the area that used the oxy acid to.

Randy

[Spinner]

Sponge it on here too. It doesn't take much as it's a bleach made for lightening wood products. Leather being more porous will take it easier. Here's a pic of a test panel I did with my latest batch (always test a batch of O.A. out to determine it's strength before use). Be sure to wear gloves when applying it.

Hopefully you can see it in the picture, but the left side is after Oxalic and the right is untreated. In person, the left is nice and even colored whereas the right is a lighter color and slightly splotchy.

[mendedbowl]

hello Randy,

can oxalic acid damage leather in any way, if it's left on too long or if too strong of a solution is used? can it be used to bleach leather?

thanks,

ken

[Randy Cornelius]

I have never had any negitive results using it. Think of it as a cleaner, not a bleach, I don't think you can bleach out a piece of leather with it. It will clean and bring out the natural color.

[Spinner]

You actually could if you kept applying it. It's normal use is a wood bleach and given enough applications and time to penetrate in heavier concentrations it will make walnut look like a stained maple. For our purposes we don't take it that far or use as heavy of a concentration though (usually) so it acts more like a stain remover.

To give an idea of how far it can de-color here's a woodturning/carving I did a few years ago with birch (yellowish tan colored wood) and numerous applications over 3 days of Oxalic Acid. They piece has not been dyed or colored in any way, simply bleached with O.A. & sealed:

[terrymac]

Thanks for the help!! I am also assuming this would be done prior to adding any oil. One more quick question, are you buying crystals or can you get in a premixed liquid?

Terry

[Spinner]

Thanks for the help!! I am also assuming this would be done prior to adding any oil. One more quick question, are you buying crystals or can you get in a premixed liquid?

Terry

Yep, before oil...the O.A. will dry out the leather some so a good oiling after will help rejuvenate it. Only way to buy the 'real' stuff that I know of is in crystal form. I prefer it that way as you don't know how concentrated the pre-mixed stuff is. With the crystals you can mix as thick or thin as you like to achieve different results.

[JHayek]

I use oxalic as a cleaner prior to oiling. I have heard others say it is a bleach as spinner said but I would think it would ave to be extremely "hot" and even then there are limits of what anything can do. As far as application goes I use a piece of woolskin that i trim to make pad roughly palm sized. I apply a fairly light coat and have not had any unwanted effects on the burnishing of the tooling, again there are limits. Trial and error are effective teachers. A plus to using oxalic is that it seems to open the pores of the leather to allow it to take oil more uniformly if you are using olive oil (if using neatsfoot nothing but more trial and error will give satisfactory results).

Hope this has been of some value to you.

Jon

[terrymac]

Again, thanks for all the help. As a side note, I have started using Bee's Natural Saddle Oil. I used neatsfoot oil, but I wasn't happy with darkening affect I was getting. One time I tried extra virgin olive oil, and again was not pleased. I had read somewhere that the Bee's product would not darken, and they were right. If anything, it seems to give the leather sort of golden hue. I really like the way it works.

Thanks,

Terry

[Tannin]

Beautiful carving/sculpture Spinner. I looked into using oxalic acid last year to remove many deep tannin stains from a large oak dough bowl that I carved (the staining probably occurred because I'd soaked the blank a long time - perhaps too long - to keep it as green and then continued to soak it between working sessions). Having seen you results, I might now give it a go - so thanks for sharing that .

[electrathon]

No one has mentioned this so I will throw it on. Oxalic acid is pretty harsh. Read the MSDS on it. If you are going to use the stuff, wear gloves and keep it off of your skin.

[Tannin]

Good point. I generally avoid using harsh chemicals, including organic solvents (such as turpentine), as far as practical. Oxylic acid is the poisonous acid found in rhubarb leaves: stronger than white vinegar (which I tried) but not, I think, as strong as battery acid, etc. Looks like gloves & glasses would be prudent.

http://en.wikipedia.org/wiki/Oxalic_acid

Edited July 30, 2014 by Tannin