oxalic acid How?

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stravaig03

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I've read about people using oxalic acid to clean stains from wood and restore as new.
My problem is a new oak floor unsealed, with blue coloured water marks from a radiator. I have some oxalic acid crystals but do n't know how to use them. Tried the index for past 3 years but no joy.
Any practical experience would be appreciated
 
Just as satisfactory is to shake up some crystals with water in a small bottle to dissolve them. Keep adding crystals til a few are left out of solution - you'll then have a concentrated solution.

If the surface you're treating is horizontal, just paint the solution on, and wash off after about 10 minutes. Repeat if necessary.

For sloping surfaces it's best to thicken the solution. Pour some off, and mix with a little wallpaper paste. That creates a nice gel which sticks to the surface til you wash it off . . .

Have fun!
 
If you need to apply further applications you can increase the concentration by heating the container in a water bath and adding more crystals. I use a jam jar in a saucepan of water near to but not boiling. Use gloves and protective clothing and if there's any risk of splashing use eye protectors.
 
For slopes, tissue paper is the easiest solution. Soak the paper in the solution and stick it on. Press it every minute or so to bring fresh solution to the offending spot.
 
I have seen suggestions of a 10% mix with water which will be very weak compared to the suggestions above. It being an acid, would the concentrated versions above present any potential probs for he surface being cleaned ?
 
The classic boat recipe is 25 grams to 500cc of water. Warm water helps; you can add more crystals for a stronger solution. Some people add wall paper paste to stop run off.

There is a potential problem that while it attacks the stain it also bleaches the unsealed new oak around it so that gets lighter. It would be useful to try to contain the solution only to the stained area to start with - plastercine?
 
Oxalic acid is an extremely weak acid even at molar strengths. It's always worth testing any cleaning solution or solven on a small unobtrusive area first though.
 
[ QUOTE ]
Oxalic acid is an extremely weak acid

[/ QUOTE ] While oxalic acid may be classed as a weak acid it is in fact one of the strongest of the weak acids, pK = 1.27, top of the list in fact in Kaye and Laby
It should therefore be kept off anything that might be susceptible to damage by acids. Any residual acid can be neutralised with sodium bicarbonate.

Also remember that it is toxic. It and its solutions should be properly labelled and stored out of sight and reach of children.
 
Why is the stain BLUE? maybe we should be thinking of another solvent, rather than a standard bleach. if the oak has been treated in some way before it was layed and has reacted with something in the heating system (like fernox) it may exascerbate the problem by hitting it with another acid....
 
Steel and iron notoriously react with oak (tannic acid, I seem to remember, but no doubt VicS will give us proper chemists' description soon). The stain is blue or blue-black.

Later: apparently it was once used a method of ink production.
 
A chap who used to look after our boat gave me the tip of adding to the normal dilution , a little washing up liquid to help it spread better and also clean off easier.
It always seemed to work!
 
[ QUOTE ]
Steel and iron notoriously react with oak

[/ QUOTE ] Yes that's right. I don't know about chemistry, that was in O level woodwork. Always assemble oak joinery with steel screws, 'cos they are strong, but then replace them with brass.

My "Woodworkers Pocket Book" (ISBN 0 237 35195 1) suggests 1 oz of oxalic acid in ½ pint of hot water. It says apply with a rag, several applications may be needed. It also says wipe over with borax (1oz in ½ gallon).
 
Don't mix it with wallpaper paste unless you are going to remove it before it dries, in which case it probably won't be on long enought to do its cleaning job. It took me half a day to get dried wall paper paste out of my woodwork ! A local chemist will order the acid for you. Big box is a tenner
 
[ QUOTE ]
A local chemist will order the acid for you

[/ QUOTE ] Pharmacist I guess you mean. Some will, some won't but you can get it from AGWoodcare
Tomiso already has some anyway.


Billjratt [ QUOTE ]
Why is the stain BLUE?

[/ QUOTE ] That's the colour of the reaction product, whatever it is.
Fernox descalers might be acid but not any conditioning chemical in the system while operating. I'd expect those to be a bit alkaline.
 
Id always wondered what would happen if the wallpaper glue dried!

I use oxalic acid to take out the black stains on the teak i mix it with water 1 gm to 10ccs and brush it on with an art paint brush,whash off with the hose
 
I've tried using the crystals ordered from Boots (£5 lighter and 5 days later, etc) but find the Wipeout fibreglasss cleaner, which is oxalic acid based, far easier to use although at £10 a pop it's not cheap. It mixes quite well into an abrasive paste and feels quite satisfying to apply. Oxalic acid from disolved crystals requires more patience. <span style="color:blue"> </span>
 
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