How to Remove or Lighten Stains on Wood using Oxalic Acid

In this video Simon demonstrates how Gilboys Antique Restorers use oxalic acid to remove stains and marks, often without the need to sand the surface.

The best way to remove stains from wood furniture is by using oxalic acid. Professional furniture restorers have been using this very safe and easy to apply treatment for decades. Oxalic acid is very effective at removing food and drink stains, including spilled red wine and water marks.

In this easy to follow video guide, I describe how anyone can use oxalic acid to remove unwanted marks from their wooden furniture.

I've been restoring furniture since I completed my apprenticeship in 1991. Establishing Gilboys restoration early in 1994 with the help of HRH The Princes Trust.

Video Chapter Index
00:05 Introduction
00:23 Preparing the bare solid oak for treatment
02:00 Mixing the oxalic and washing soda
04:10 Applying the oxalic with a sponge scourer
08:02 The results of using the oxalic on oak
09:00 Treating mahogany with oxalic
09:50 Stripping the mahogany
11:30 Preparation before applying the oxalic to mahogany
12:50 Applying the oxalic acid to the wood
15:30 washing soda reaction with oxalic
17:13 The difference between modern veneer and an antique veneer
18:12 Close up of washing soda reaction
20:12 Results after 24 hrs
20:44 Using a small artists brush for detailed, spot removal of stains and marks
22:09 How to apply french polish (shellac) to show off the wood
23:57 Applying the polisher's fad to the wood surface
24:32 A french polishers mop
24:51 Showing off the mahogany finish
25:47 Applying a fad to the treated oak
26:10 Close up of the sealed oak
26:25 Conclusion

[McSlobo]

No point in putting soda after acid after soda after acid because you'll just waste good stuff! Just let the acid crystallize on the surface, wipe a way (could be re-used) and neutralize only afterwards.

[MsShawnPhx]

wouldnt baking soda do the same thing as soda crystals? Why keep neutralizing why not neutralize at the end once you get to the point you want?

[adrianrichards]

Just came across this channel today what a Find ! …trying to find out how to restore / enhance the finish on an old Chinese / Japanese Table that my sister bought back from HongKong some years ago its beautiful - just ( in my opinion ) needs a bit of TLC to the finish on the table ….. hopefully I’ll find a video that shows the way

[FREDRIKGIERTZ]

Quick comment, if the black ”stain” comes from the contact with iron, neutralizing the acid with some alkaline substance will actually bring back the stain. The reason for this is likely that the iron oxide (likely what it is?)
reacts with the acid, but if you neutralize it, large parts (if not all) of the iron will return to the blackened shape. In this case, wash of the excess acid with water, dry the wood and remove any dried oxycillic crystals instead.

[mrstandfast]

Very informative and enjoyable as always. Great to see that you're still enthusiastic about your work; ".... I couldn't resist putting some polish on ...."
I sometimes use a thick oxalic acid paste to remove years of oxidisation from old brass hardware. It makes final cleaning and polishing so much easier.

[marcelomendez]

Simon I have a question regarding the particle board being swollen due to water. What can be done about this? I made the mistake of adding the oxalic acid solution directly to a piece of the wood, and bubbles formed shortly after. Thank you. You are the premier restorer on youtube.

[ToniDunmow]

Thanks for this video. I used some oxalic to remove a stain from the top of an Ercol dresser, which worked great but a few weeks later I have a white dust/powder residue on the surface. I didn't know about neutralising with the soda, but I did wash over with water a few times, I am guessing the residue is the oxalic still leaching out. After watching this video going think I need to try neutralising and see if that helps.

[hawkercnc]

Oxalic acid is much stronger than acetic acid (vinegar), hence it’s use to clean stuff and react with ink or whatever to remove it. Strong organic acids such as hydrochloric would work faster, be much more dangerous for the user and difficult to remove the residue. Therefore it is not used domestically. It seems strange to add the acid then stop it working with alkali, then to keep repeating the process. A salt with be produced in and on the surface of the wood, which needs to be removed later. It would seem logical from a chemical point of view to allow a small amount of acid to work for longer until the desired result is achieved. Perhaps a piece of polythene to cover the area would keep the acid in solution rather than it dry out back to crystals or a light spray of water. Removal of acid can be done with water or a little bit of alkali. Oak is acidic with tannic acid within it. If steel wool is used and minute fragments are left in the wood surface and a finish applied, overtime black spots of ferrous tannate will form. Care is needed using steel wool on oak. Useful video, got me looking up the chemistry. Thanks

[SneakersKicksCreps]

Lovely video just the information I was looking for thank you.

[rossr]

I've used this acid to treat stained swimming pools, tannins from leaves generally. Amazing stuff. Easy to over-do it though, heh. Kills Ph bigtime. Results before your eyes

[RecipeArchaeology]

I have a butcher block countertop. A wet towel was left on it overnight and now it has a dark water stain. Would Oxalic acid work to get rid of the dark stain? It was in excellent condition before the water stain and now I'm worried that my beautiful countertop is ruined.

[magnuswootton]

theres an oxalate salt which is very similar to plaster, so u can make a plaster from that oxalic acid as well!!!

[dickiedogs]

fab video..nice and simple and to the point...Many thanks.!!!

[polarbearsrus]

That didn't make sense... aren't you putting the acid on it to bleach it? Then why add the soda crystals to neutralize the bleach, I'm confused. Thanks for sharing.

[marcellebradbeer]

What did you strip the mahogany surface with before applying the oxalic acid?

[michaelmercury]

Hi, please using oxalic acid to clean wood worktop stains from the black rubber feet of an appliance left on the surface, the legs have left a tattoo of marks. Please can I speed up the drying process with a hot air gun before applying a second or third round? Is it best to let the oxalic acid solution dry before going at it again? Many thanks

[ARTCHANIFY]

I used this technique on a stripped oak staircase with some black water stains but when I applied the soda, large areas turned dark that weren't before. Now I have to go back with the oxalic acid? It looks worse than before!

[gowergalteechick]

Would this work to take out grey wood oil stain from entire kitchen table? Bought the table in farmhouse grey colour but I want to strip it back to the original ash colour

[comonoamarunaflor]

Hello,
I have a stain of black grease which has stained the wooden floor. Do you know if this would work on the floor stain?
It only has an organic thin coating
Thanks

[dianebroadley]

Is there anything that oxalis acid doesn’t work on? I bought an old pine table that was someone’s art table or something. If there’s oil or grease would that not shift?