Oxalic acid is the stuff to use to bleach out black water staining. It comes in crystal form that you dissolve in water. It is poisonous so wear gloves and stare carefully.

It wont touch colour change due to UV exposure – thats 80 grit and elbow grease! On an 80s boat there should be plenty of veneer to play with provided no-one has hit it too hard before.

It would be helpful to know more about exactly what discolouration your boat is suffering from.   Can you post some photos?

Having tried wood dye on bare wood which has previously been painted or varnished I would counsel against it.  My experience in 2005 on a GP14 transom was that although the wood looked to have been stripped back to bare wood,  it seems that in fact some  –  but not all  –  of the pores in the wood were still blocked by hardened paint or varnish,  even though not visible,  and this blockage was not uniform;   the result was that when the wood was stained it turned out extremely blotchy and unsightly.

My second thought was to mix a stain in with varnish before applying it.   This can work,  reasonably well,  but there are some issues.

First,  the resulting stained varnish is indeed still very transparent,  so you can still see the beauty of the wood through it.

Second,  if you use International products,  their Mahogany Wood Stain is no longer marketed in the UK.   The last I heard,  it was still available in Germany,  but that was a few years ago.    When I learned that it was being withdrawn I snapped up the last two tins of it from my local chandler,  and I still have one of them;   but,  sorry,  I am keeping that in stock for my own future use.    However it is possible that you may be able to obtain some,   by persistence,   via either the manufacturer or online searches.

Third,  International’s Technical Helpline confirmed to me that it can be mixed into Schooner varnish;   they had no information on whether it could also be mixed into Perfection Plus varnish,  but I tried it and found that it did indeed work.   Be aware that the wood stain also acts as a powerful thinner,  so you should not add more than about 10% (at maximum) by volume,  the resulting mix will go on very thinly indeed,  and if you try to brush it on thickly it is liable to run;   so you may need several thin coats to build up the desired colour.

Fourth,  it is possible that a different manufacturer may offer a high quality yacht varnish and a compatible stain;   I am not aware of any,  but I have not had occasion to do the research.

Fifth,  when I was making my enquiries (in 2005 for conventional finishes and again in 2006 for 2-pot polyurethane (for a different boat)) I drew a blank with Rustin’s.   Quite understandably,  they were unable to advise on the compatibility of their wood stain with another manufacturer’s varnish,  and they do not manufacture a yacht varnish themselves;   or at least they did not at that time,  and I am not aware of them having done so since then.    So it might or might not be possible to mix it in with your preferred deck varnish;   but there is nothing (other than cost,  if the material ends up being wasted) to stop you experimenting on some test pieces that are not part of your boat.

Hope this helps,

Oliver

• This reply was modified 5 years, 9 months ago by Oliver Shaw.

Thats frost damage.

You shouldn’t need to treat it, it should sand out after you’ve stripped the varnish back.

That looks to me to be a case of the varnish lifting because water has got underneath it.   Frost damage,  as identified by Chris,  is another closely related cause.

I think you will find that sanding down and then revarnishing is amply sufficient,  without needing any colour restoration;   indeed my guess is that you will then find that the finished job is slightly darker and richer than the surrounding wood,  because it will be a newer surface which has had less exposure to UV.

Given that you know that the problem has arisen,  that the likely cause is water getting under the varnish,  and that the boat is from the 80s,  a likely reason is slight movement of the wood,  cracking the varnish film.     I would therefore be very tempted to use a top quality conventional varnish,  rather than a 2-pot polyurethane,   because it is slightly more tolerant of slight movement of the wood.   In any case,  if the existing finish is one-pot (of whatever persuasion),  or if you don’t know what it is and cannot be 100% certain of it being two-pot you cannot use two pot on it anyway.

One of the best conventional varnishes in my book is Schooner,  by International Paints.   Not Schooner Gold,  which is not the same product at all;   I have once tried it,  decided that I didn’t like the way it flowed on (or didn’t flow),  and spoke with their Technical Manager who told me that it was designed for a particular market (for people who were not used to varnishing),  and he agreed with me about its flow characteristics and said that if I liked the original Schooner he was not surprised that I did not like Schooner Gold!    Schooner is a tung oil varnish,  with a deep amber colour,  and amongst the conventional varnishes in International’s range it has possibly the optimum combination of  gloss and durability;   it is not quite as hard as their Perfection two-pot polyurethane,  but if there is any suspicion of movement of the wood it is a safer bet to use.

One tip is worth passing on;   never use the varnish straight from the tin,  because as soon as you open the tin the surface will start to harden,  and eventually form a skin.   Instead decant the amount you expect to use (plus a small margin of safety) into another container,  and immediately re-seal the tin.   Then when you come to apply each of the successive coats,  what is left in the tin will still be in fit condition to use;   each time decant off what you expect to use on that occasion,  and immediately re-seal the tin.

However on bare wood I would first apply 4 coats of a varnish primer:  International’s Clear Wood Seal Fast-Dry.   That mouthful of a name is indeed descriptive;   in sumer conditions one can apply four coats in a day.   Then four to six coats of Schooner on top.

International Paints happens to be the brand with which I am most familiar,  but there are other equally good brands of yacht paints and varnishes,  e.g. Blakes,  Hempel,  Awlgrip,  and others.   I am not holding a candle for any one brand over its competitors,  merely describing what I would use from the range with which I happen to be most familiar.

Photo shows my erstwhile GP14 Strait Laced in 2005,  newly finished in Toplac and Schooner,  as an example of the final finish.

Hope this helps,

Oliver