How to Remove or Lighten Stains on Wood using Oxalic Acid
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- Опубліковано 27 вер 2024
- 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.
You can now buy Oxalic Acid on our website: bit.ly/3QZIon9
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
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.
Agreed, that didn't make sense to me either.
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?
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.
Hi Marcelo.
There's not much that can be done with swollen particle board. It normally means the piece is unrepairable.
There is one way of recovering it and that's by digging out the board in the affected swollen area and then filling it with a two part wood filler, which you then have to sand smooth to the level of the veneer. The next process is hand colouring and graining the repair to make it look like the surrounding veneer. And finally refinishing the entire piece.
It's success depends on the location of the repair and how artistic the person is carrying out the repair to trick the viewer into believing its real wood. 🤨
I have a friend who successfully restored particle board by soaking the area with "super thin" CA glue then when dry, sanding the area back to flat.
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.
Thank you. What body do you add to your oxalic to make it into a paste?
@@GilboysRestoration Simply water. I apply the paste with an artist paintbrush, and wash it off 10 minutes later. The oxalic acid I use is an American product sold as a powder under the name of Bar Keepers Friend. There's also a cream version, but it seems less efficient for my requirements. I've used it on wood, but with cold water. I shall use hot water just off the boil next time as your results appeared to better mine.
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.
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.
I dealt with a similar issue - a wet rag left on an oak board without paint. Oxalic acid removed the brown stains. But the tricky part is that it then has to be washed off with water, which will easily make the stains again. I tried drying the water with paper towels right after washing it to get as much of it off as possible, and then drying the rest with a fan. The result is significantly better than it was before.
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
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
Ph?
theres an oxalate salt which is very similar to plaster, so u can make a plaster from that oxalic acid as well!!!
Thank you!
Lovely video just the information I was looking for thank you.
Thank you. Due to demand, the oxalic acid will soon be available on our website. ✅
Nice one Simon, keep um comin !!!.
What did you strip the mahogany surface with before applying the oxalic acid?
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!
Wow! I have never experienced this. I wonder of there was something dormant in the oak that has reacted with the alkaline in the soda? I wonder if anyone else has also had this reaction? Did washing over with oxalic again cure the problem?
Kind regards
Simon
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
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.
The results speak for themselves. It works. ✅ although I'm not a scientist. 😄
I understand that washing over with the soda crystals neutralises the acid. But at the time of applying it, it appears to catalyse the process of bleaching.
You can actually see the colour lifting off the surface.
Also I like to know that when I do use the soda crystals the reaction has ceased.
In the past we have applied too much without neutralising, returning the next day only to find it's gone too far and removed too much colour.
Can household bleach be used over water stain wood
No. There are products for water stains. Look them up on the internet.
Regular bleach never goes away.
So it didn't work, did it? The ink stains weren't actually removed. I would suggest looking for the appropriate solvent. There are many used in inks, so finding the correct one could be a challenge.
Would you use this to bleach oak? Have a fantastic 20+ yr old solid oak kitchen that needs some TLC. Is bleached white oak with PU varnish, and am trying to find the right finishing technique to replace a couple of small parts.
Hi. You would need to strip off the polyurethane first. But yes, it will work well on the doors. You must strip the old finish for it to work. ✅
He says multiple times that the first board showcased is oak.
I’m working on a dresser right now that I’m taking down to the original wood and then just applying a clear polycrylic too. After stripping off 3 coats of horrible orange/brown paint and a layer of stain, I’m ready to lighten some dark spots on this light wood. My question is whether or not a should condition the wood a little before adding the poly. I’m worried that all the stripping and oxalic acid has dried out the wood and I really want this piece to last forever. Help 🙂
Hi Careen.
I'm not sure what conditioning the wood is? If you are applying a polyurethane finish, I would just dilute the first coat by around 30%. Then the second coat by 20% and then The last coat by 10%. But that's based on a traditional oil based polyurethane.
If it is water based, and many are these days, I would read the side of the tin to see what they recommend. ✅
Diluting the first coat will help it to bond to the surface. 🙂
kind regards
Simon
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
Digital watch artificial lighting. Pshh
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?
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.
Hi Toni
You are right. We have had this happen a number of times in the workshop. The oxalic needs to be neutralised. I would also recommend wash over the surface with methylated spirits.
If you are able to, leave the surface to air dry for a few days before commencing on the finishing process.
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
Rugby?
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
Would this process work ok on wood veneer? I have a gplan sideboard with some marker on top. Thanks
Question: Can you paint the oxalic acid only on specific areas? I stripped an old primitive cupboard that I thought was oak. To my horror it is poplar. The panels on either side had these huge dark green steaks in them. Will the oxalic acid remove these dark green streaks? I don’t want to lightened the rest of the wood. HELP! How about using masking or painters tape on the edges of the green to keep it from bleeding into other areas?? Please help!
Often putting poplar boards in the sun will make them go from green to brown, at least for newer boards. I haven’t seen green on older poplar boards.
Thanks for sharing
My pleasure.
fab video..nice and simple and to the point...Many thanks.!!!
My pleasure