Badly stained wood - Oxalic Acid?

[Wandering Star]

I recentlly bought an older neglected boat which had had water above the sole for quite a while. Now dried out, the cabin sole and sides of the interior woodwork in the main cabin (saloon) are heavily stained and darkened to the extent of the water ingress level above the sole - about 4”. I think the wood is solid teak but I might be wrong. Despite the staining the wood seems solid and the boat is of GRP construction, a Rival 32.

Am I too optimistic to believe I can restore the darkened wood to a nice bright finish to match the rest of the undamaged wood by bleaching wth Oxalic acid? How do I thicken the acid solution so it sticks to the wood whilst it performs it’s magic rather than just running into the bilge? is there a better method of restoring the darkened wood’

Would it be more sensible to use veneer glued over the damaged wood instead of wasting my time trying to get rid of the staining? How difficult is it to apply veneer?

Any other suggestions? The boat in question isn’t arriving until Thursday so I can’t take any pictures specifically of the staining until it arrives, but (if I can manage it) I am posting a general picture of the saloon area which if you study it carefully should show, not very clearly, what I’m talking about. Don’t concern yourself with the state of the cabin, she’s been completely neglected for 10 years and I know she’s in a mess! The challenge is bringing her back to her former good condition.

just to add - if anyone can identify the type of wood correctly, you get a bonus point.

 

[VicS]

You will find some useful info on the use of oxalic acid for stain removal on the AG Woodcare website. (thickening is not required.)
Oxalic Acid Crystals

They seemed to have expanded their range since I last looked at the site. There may be other products of interest

IIRC many years ago PBO reviewd teak restoration products. Maybe someone will have kept the article and can pass on its findings

 

[tillergirl]

If it is solid wood, oxalic acid would work. If veneer, I fear re-veneering is a better option.

With oxalic acide you need to add patience! The below is repeated applications with light sanding.

Laying Up 2011 038 by Roger Gaspar, on Flickr

Laying Up 2011 040 by Roger Gaspar, on Flickr

Misc 2011 048 by Roger Gaspar, on Flickr

 

[Boater Sam]

Try mixing Oxalic acid into wallpaper paste, it will be a s thick as you want. I have used oxalic for removing ferrous rust marks from timber with good success.
Good luck.

 

[Tranona]

Suspect you will be trying a range of techniques of which oxalic acid will be one. You can only decide how best to restore the wood when you strip it back. As suggested you can do more with solid wood than with veneers as there is more "meat" to work with. My approach on the 1979 boat I am restoring is to strip using either heat or chemical stripper back to bare wood. Then you can see the extent of the staining and rot if there is any. stripping with a scraper will remove some then you can take a view as to whether it is worth trying to bleach it out starting with dilute bleach for light staining and stronger for heavier. Expect you will end up with patchy areas and then you can consider using stain to get a more even finish. You may, however find that whatever yu do with areas that have been submerged in dirty water you can never get it back and painting is the only option short of cutting out and replacing with new.

Faced ply is different as even good old ply has fairly thin surface veneers which stain easily. Areas like berth fronts and even lower bulkheads look good white and bulkheads higher up generally fare better or can be reveneered. I deliberately adopted a white an veneer scheme, not because the lower parts were bad although the aft bulkhead was but because most of what is white in the first 2 photos below except round the galley was formica veneer which was popular in the 70s. This scheme was based on a previous boat of similar design which was originally very dark ply. I have not done all the formica yet - still the berth fronts and the forecabin. the solid wood when restored will look good against the white.

 

[Wandering Star]

Thanks for the helpful replies. I’ll start with Oxalic acid treatment & see how it goes. No suggestions for the species of wood used as per the picture? What wood has beenused in your Golden Hind Tranona? Mine looks similar but in a dreadful state!

 

[Tranona]

Mixture of teak and mahogany. All the trim around the locker doors is teak as are the posts but other trim round the bulkheads is mahogany. All the new wood I am adding is mahogany from the same source as much of the trim in the last photo of my Eventide which I did in the 1990s using a job lot of mahogany I bought in 1982 from a conservatory factory that was closing down -( £50 the lot!). Down to the last 2 bits now one of which (70*70) will make the new engine beds.

If your Rival was factory completed I would expect much of it to be teak. I remember seeing them in build in the late 70s and they used a lot of teak and teak faced ply. I think you will struggle to get that ply veneer back to the point where is will look good varnished. Lot of sun bleaching which is difficult to get back to a consistent colour, but the solid trim should come up OK. Worth looking at fellow forum member Concerto who has posted good videos on restoring his Fulmar, particularly the bulkheads.

 

[ashtead]

Clearly Tranona is a wise and experience source here but if you have a Westerly as said Concerto would be worth meeting /speaking to maybe if you plan to be at a boat show say etc. I visited him last SBS and it’s certainly worth a call to him I guess.

 

[prologica]

If it is solid wood, oxalic acid would work. If veneer, I fear re-veneering is a better option.

With oxalic acide you need to add patience! The below is repeated applications with light sanding.

Laying Up 2011 038 by Roger Gaspar, on Flickr

Laying Up 2011 040 by Roger Gaspar, on Flickr

Misc 2011 048 by Roger Gaspar, on Flickr

Lovely work Roger!

 

[Concerto]

Strangely, I prefer to use cheap supermarket bleach to remove staining, not oxalic acid. This was advised to me many years ago for cleaning mould in foam backed vinyl. I also know an antiquarian bookseller who cleaned and sold antique maps and engravings who used cheap bleach. The cheapest bleach does not have any perfume added compared to branded bleach.

Naturally, no treatment will work if the surface still has any finish on it. It was probably originally protected with lacquer, but may now have had some varnish applied by a previous owner. Either way, the varnish can be striped chemically, but the lacquer will not get touched. So you will have to manually remove the finish. I have found the easiest method to remove any finish is with a 1½" chisel that has been ground on a small diamond grinder (about £20 on eBay or £15 from Lidl or Aldi) but leave the curl on the cutting edge. This curl works like a cabinet scrapper and much quicker to keep sharp. When stripping the finish, watch the colour of the dust. If it is creamy in colour, this is the finish. If it goes brown, you are removing wood, so stop. Once a panel has been srapped, now gently sand with the grain with 320 sandpaper. Again watch the dust colour. Now wipe the surface over with a damp cloth. If water is absorbed, all the finish has been removed. If not, allow to dry and sand the area that did not absord the water. Now you can start bleaching.

Initially I would start with the darkest patches using a 4 parts water to 1 of bleach. Leave for about 15 minutes and wash off with lots of water and dry off. Continue repeating this until you are happy with the colour of the wood. Then you are ready to apply a new finish. On my Fulmar I used the same lacquer that Westerly used. It is Morrells 450 acid catalyst high build up low odour lacquer with 30% sheen. Lacquer has many advantages over varnish. It can be applied with a brush. It is fast drying and 3 or 4 coats can be applied in a day. It is very hard wearing. Nomally I will only mix a maximum of 60ml at a time and keep the brush in thinners between use, only fully cleaning it every few days. Cost wise it is far cheaper than varnish. 5 litres of lacquer with hardener and 5 litres of thinners is about £60. Morrells are a trade supplier to mainly the furniture industry and have branches all over the country. It is not a counter stock item, but will be brought in overnight. Best to phone the order and collect the following day.


This shows the difference between the completed starboard side to the port untouched bulkhead.


This shows the creamy dust to the top and wood colour dust at the bottom.

Naturally all of this does depend on any veneer still being fully bonded. If the plywood is treaking down due to prolonged immersion in water, I would advise painting the panel section white and having wood trim showing, as per Tranona's post. This may also be a lot quicker to complete. With any old boat, mine is 41 years old, you do not have to keep it exactly as it was built. I was fortunate, that the minor bits that had suffered some delamination of the veneer, I was able to cover with a wood strip and stain it to match the main timber. Unless I point it out, it looks original as very few people know how it should look.

Best of luck with your new boat. I would be happy to answer any specific questions that I have not covered.

 

[William_H]

I love bleach for all sorts of cleaning. Unfortunately I have a history of accidents with bleach on clothing and even bathroom mats. Last effort was when I sat on a rag used to bleach inside of boat. Ruined a pair of shorts. Big brown what looks like a stain but is actually colour loss from fabric. Just be careful. Wear old clothes and gloves. ol'will

 

[dansaskip]

Strangely, I prefer to use cheap supermarket bleach to remove staining, not oxalic acid.

The advantage of using Oxalic acid is that is does not lighten the colour of the wood - unlike bleach which will 'bleach" out any colour in the wood - it's in the name.
So I would go for oxalic acid every time.