How to lighten mahogany?

[Captain Crisp]

Hi,
Last season I damaged a section of my mahogany carriage top and had to sand it back. It's now coming out very dark red.
Any advice in using a lightener to get to blend in?
Thanks,
Crisp

Some images below:

Desired finish:


Damaged area:

 

[Easticks28]

Hi,
Last season I damaged a section of my mahogany carriage top and had to sand it back. It's now coming out very dark red.
Any advice in using a lightener to get to blend in?
Thanks,
Crisp

Some images below:

Desired finish:
View attachment 114536

Damaged area:

View attachment 114537

Firstly is the woo completely dry ? It could be darker because of wet, but I know of no way of lightening a patch like this. Ether accept the difference in colour or be prepared for a strip of all the varnish back to bare wood and start again.
I am planning to do this on my own boat next winter.

 

[Daydream believer]

Liberon or Rustins wood bleacher. I think that my polisher preferred Rustins- I left it to him. Then I seem to recall he used to neutralise with vinegar.
He was a real old tradesman & also used some weird chemicals - Oxalic acid ( mix with wallpaper paste on vertical surfaces) comes to mind but I may well be wrong on that one. You could just try a strong household bleach but I think it has to be a special formulation - hence "wood bleach"

 

[Scotsailor]

I wouldn’t worry. It will lighten with sunlight given time.

 

[ip485]

A lot depends the cause of the stains.

If it is likely to be water ( I would think it is ) oxalic acid is probably your best bet.

Acutally stain in the wood and a conventional wood bleacher, effectively hydrogen peroxide and cuastic soda is maybe a better bet.

The answer will be to try a section and see how much of the staining you can remove.

 

[Poignard]

Trying to bleach the raw mahogany to exctly match the weathered varnish might involve more effort than stripping the lot off.

And, even if you succeed, when the yellowed varnish has eventually to come off you will have to go through the bleaching process again.

 

[grumpy_o_g]

I was going to suggest drilling holes in it when I saw the title but thought that might not be appreciated. It won't be much comfort but, many decades ago when I was a teenager earning spare cash in the Burnham boatyards the accepted practice was to either replace the wood (a lot cheaper in those days) or to darken the rest of the wood. I would second the guidance about making sure it's absolutely dry though.

Oxalic Acid can be used on some woods but I've never seen it used on Mahogany. There's a little bit of guidance here How to remove wood stains and they seem to think it can be used.

 

[Daydream believer]

Why not strip the lot & go for a nice Sikkens Cetol filter 7 plus instead. Will last better & give a nice rich finish

 

[Blueboatman]

Concurring with Daydreaming B’s lead, I would suggest if you have some time and the requisite patience, you find another piece of overly sanded , red ( unoxidised ) mahogany ( I know there are gazillions of so called ‘mahoganies’ out there) and try wiping neat bleach across it, let it dry , repeat .. get a sense of how much bleaching is likely to move you in the right direction..

OXALIC brings out the colour in teak cockpit and grey handrails , you could try that too
Astonish mold remover ( £1 a pop, cheap as chips ) is another one to play with ..
A cheat would be to paint the offending area with very very dilute white paint too !
So many of these arts only are effective with lots of practise ...
White Vinegar with iron filings ( wire wool ) ‘ rust ‘ in it is another one...
I know A Very Little Bit but not A Lot? I’m afraid ..

Here’s an American link :
Bleaching the red out of mahogany is about 2/3 down page “ Blond Mahogany “


USING WOOD BLEACH

 

[Tranona]

It is not the cleaned bit that is dark, but the rest that has been bleached by the sun. Only long term answer is to do as suggested and take the whole lot back to bare wood, sand and oxalid acid to get rid of most of the bleaching and then perhaps use some stain to get it uniform. Us e finish with good UV (not traditional varnish). Woodskin is quick, easy and effective. Cetol filter Plus also good and even better with a base coat of Cetol HLS.

Lot of work getting old faded mahogany back to good even colour and then protected properly, but once done you can forget about it for a few years, particularly if you use your winter cover every year if you are not using the boat.

 

[upcountry2]

Tranona is spot on, I have done it for years like this, no short cuts I am afraid, good results can be had but it requires time and patience. The more you do the better you will get....

 

[Keith 66]

Most people spend years trying all sorts of varnishes & unguents to stop the lovely dark red fading....

 

[ip485]

I think the O/P is probably happy with the lovely silver tone that the wood has developed, rather not so keen on the "fresh appearance" of the damaged section but I could be wrong.

 

[ip485]

BTW I am very proud of my teak toe rail. It has gone through various stages of varnish and other finishes and ended up with bare wood and Boracol every six months. In some ways I loved the colour and finish when freshly sanded back, but I knew it wasnt going to last, unless perhpas it was epoxied and varnished. Having been there, it is never going to happen again. It is just such an enormous job when it needs redoing, in the order of a solid weeks work. As you can imagine I have come to appreciated the lovely silver and easy maintenance that comes with it. I appreciate in the case of the O/P this is not an option, and so I apolgise for the continuance of the sllight thread drift.

 

[Rappey]

It is not the cleaned bit that is dark, but the rest that has been bleached by the sun

So well put ☺.
In my own experience the wood gets very light in colour and the varnish then starts crumbling.
If it's still sound I would just attend to protecting the bare wood and get on with enjoying your boat as it will get lighter.

 

[Tranona]

I think the O/P is probably happy with the lovely silver tone that the wood has developed, rather not so keen on the "fresh appearance" of the damaged section but I could be wrong.

Problem is you cannot get patches to match the faded areas. As soon as you remove the failed coating and sand it you expose the basic colour of the wood. . The only way for the OP to get his coachroof looking good is to deal with the cause of the water ingress at the forward end, strip all the varnish off the whole lot, restore the colour as best he can and then protect as suggested. Just one of the joys of owning such a boat and there are no shortcuts in the preparation. The good thing though is if you avoid "yacht" varnish and use the products suggested you can look forward to several years of light touching up only.

The brightwork on Tranona (mostly mahogany with ply coachroof sides) was last taken back to bare wood in the early 2000s and coated with Woodskin. The boat was laid up in 2010 under a tarp in the winters and in 2019 was recommissioned. Most of it just required rubbing down and recoating. The mast was stripped again in early 2000s and coated in Sikkens Novatec/Top and stored in the open in a mast rack. Most of the coating was still intact except about one third that was on top. I stripped it and recoated with Cetol as described in post #10. It looks superb and although I have sold the boat, I expect that coating to last at least 10 years with maybe one rub down and recoat.

 

[Captain Crisp]

Many thanks for all the advice! Just to clarify there's no water ingress. The damage was caused by a loose section of cover blowing about that I had installed to protect the wood...
It looks dark in the image because I had just rubbed white spirit on it.
I am going to experiment with some bleach on an off cut, but not worry too much as I need to get on with varnishing, launching and... who knows ... Maybe even some sailing...
Thanks again all!

 

[johnalison]

The only way to get a full match would be to strip it all back, but lose some wood in the process. I would aim for a halfway result and do some light work on the bleached and stained section, settle for the ‘mature’ look, and let time do the rest.

 

[Tranona]

Many thanks for all the advice! Just to clarify there's no water ingress. The damage was caused by a loose section of cover blowing about that I had installed to protect the wood...

I was referring to the varnish coming off the corner post and the dark appearance of the front face - plus the gap between the side and the corner post. Looks very much like water has at least got under the varnish there, even if not necessarily into the boat.