Oxalic Acid

[9fingers]

I have some slight bluish-black staining in some new oak that I want to use rather than discard as it has other wanted features. I have read in several places that oxalic acid is the stuff to use as a bleach to get this out.
I've got some crystals on order but looking for hints and tips on using it.
Questions are currently:-

What concentration to use?
How long to leave it on (maybe these two are linked?)
Does it need to be neutralised of just washed/wiped off?

Any other tips?

TIA

Bob

 

[The Bear]

Bob

I followed Pekka's advise in this thread, though i found the stain "disolved" in minutes before my eyes. I could actually watch it and make a call when to stop it, and it was very black the staining.
I didn't bother to neutralise, I just rinsed with copious amounts of water, but this was an outside project.

https://www.ukworkshop.co.uk/forums/oak- ... 25265.html

Mark

 

[9fingers]

Thanks Mark,

I will try and experiment to determine the proportions of the saturated solution and post the results back here. I'll try and get a formula in terms of grams per litre of the final solution.

Cheers

Bob

 

[yellowbelly]

Thanks Mark,

I will try and experiment to determine the proportions of the saturated solution and post the results back here. I'll try and get a formula in terms of grams per litre of the final solution.

Cheers

Bob

The link The Bear put up I dissolve as much as I can in BOILING Water i.e. until you can see its no longer dissolving :wink: and then apply with either a paint brush or dish mop depending on area being treated, it will work while its cooling but is not as effective as when its hot.
Wear gloves and be very careful as it is a very strong poison in its own right

 

[9fingers]

Thanks Mark,

I will try and experiment to determine the proportions of the saturated solution and post the results back here. I'll try and get a formula in terms of grams per litre of the final solution.

Cheers

Bob

The link The Bear put up I dissolve as much as I can in BOILING Water i.e. until you can see its no longer dissolving :wink: and then apply with either a paint brush or dish mop depending on area being treated, it will work while its cooling but is not as effective as when its hot.
Wear gloves and be very careful as it is a very strong poison in its own right

Do you know if the increased effectiveness when hot is due to more active chemical being in solution or if the temperature is key to the chemical reaction with the stain irrespective of the concentration?

Cheers

Bob

 

[yellowbelly]

In fairness I've never experimented :? just the way I was shown how to use it, the hotter the solution the quicker the stain was removed but never thought about strength of solution ratio? I just carried on adding the crystals till they no longer disolved, sometimes in a glass/plastic jug othertimes a bucket and it does nt keep for later use
One other point DONT mix it in a metal container

 

[9fingers]

OK thanks,
My think was that some of the crystals would come out of solution as the saturated solution cooled.
I'll try some experimentation and see if I can draw some conclusions.
Some web references I have found mention re-heating the cooling solution, others make no mention of this.
Hopefully posty will bring the crystals tomorrow.

cheers

Bob

 

[9fingers]

I had excellent results with the oxalic acid.

Looked at several recipes and in the end followed the average of a couple of similar ones.

The mix was 10 parts hot water to 1 part oxalic acid by volume

This equates to 2.5 teaspoons (I used the teaspoon measure that came with our breadmaker) to 100ml of water which is enough to treat a couple of square feet. If you have sensitive scales 2.5 teaspoons of crystals weighs about 5 grams
So that is 20 parts water to 1 part crystals by weight.

I painted it on hot and tried to keep the wet edge following the grain but I need not have worried as after wiping off with tissues and then a damp cloth, the wood dried back nicely.

I started on some scrap first and then moved on to the stain in the table top I'm making. Prior to the bleaching it was obvious which side was which due to the stains. Afterwards I was hard pushed to see which side was which.

Thanks to those who offered information.

Bob

 

[yellowbelly]

Satisfying outcome then :wink: well done

 

[Arnold60]

Just hearing the word "acid" sounds ominous. But oxalic acid is easy to use and the safest for the home. In fact it is found in many vegetables including spinach, and rhubarb.
Perhaps its best known use is that as a wood bleaching agent.
Exterior wood tends to turn a dark gray after being exposed and Oxalic acid solutions are used to lighten and brighten dingy gray wood.
In the refinishing of wood furniture, oxalic acid can be used after stripping to lighten and soft darker stained areas befor refinishing.
a few other uses for oxalic acid are:

* Precipitating agent in Rare-earth mineral processing;
* Bleaching agent in the textile activities, wood pulp bleaching;
* Rust remover for Metal treatment;
* Used in commercial rust removers to remove rust stains from tubs and sinks.
* Grinding agent, such as marble polishing
* Waste water tratment, removing calcium in water.
* Use in cleaning and sterilizing homebrewing equipment.
* Useful as a reducing agent for photography and ink removal
* Used as purifying agent in pharmaceutical industry
* Rrock collectors,clean mineral specimens
* Remove food and rust stains from kitchen countertops, plumbing fixtures and fabric


http://makemoneyonline.net.ph

 

[yellowbelly]

:shock: REALLY why is it that you had to sign a poison register then to purchase it?

 

[SteveS]

I used oxalic acid quite successfully to remove ingrained skin oils on a musical instrument which had stained the amboyna veneers after the French polish finish had been worn away through years of playing. Finished with blonde shellac, came up a treat, and you'd never know it had previously been so badly stained.

Steve

 

[ChipsNDust]

Be a wee bit careful:

http://www.jtbaker.com/msds/englishhtml/o6044.htm

The MSDS states:

Emergency Overview
--------------------------
POISON! DANGER! MAY BE FATAL IF SWALLOWED. CORROSIVE. CAUSES SEVERE IRRITATION AND BURNS TO SKIN, EYES, AND RESPIRATORY TRACT. HARMFUL IF INHALED OR ABSORBED THROUGH SKIN. MAY CAUSE KIDNEY DAMAGE.

SAF-T-DATA(tm) Ratings (Provided here for your convenience)
-----------------------------------------------------------------------------------------------------------
Health Rating: 4 - Extreme (Poison)
Flammability Rating: 1 - Slight
Reactivity Rating: 1 - Slight
Contact Rating: 3 - Severe (Corrosive)
Lab Protective Equip: GOGGLES & SHIELD; LAB COAT & APRON; VENT HOOD; PROPER GLOVES
Storage Color Code: White (Corrosive)

It is in rhubarb, that's why you don't eat the leaves and it's no longer permitted to make insecticide out of them for your greenfly.

R