Water stain removal.

[humbug716]

Does anyone know how to remove water marks and black staining from marine ply? I am currently refitting my Osprey and before I start epoxying and varnishing was wondering if I can clean up the marks a bit.

I have been meaning to crack on with this earlier this year but I had to go and work at some minor sporting fixture this year. Now I'm worried the cold damp weather will slow me down

Thanks for any input.

 

[Talulah]

http://forum.woodenboat.com/showthread.php?7378-Black-Stains-on-Mahogany

 

[Hoolie]

+1 for oxalic acid! But be careful - it's toxic.

 

[Tranona]

Oxalic acid is the most effective. However, ply veneers are not easy to deal with if they have been damp for a long time as the outer veneer is usually quite thin and the staining goes right through. You may find you still end up with a patchy appearance and might have to use stain to get an even colour. If your boat has the usual striped sapele foredeck it can be almost impossible to get it back. Not sure I would epoxy. On my Osprey I used conventional varnish - lots of it! and always kept the boat under cover. There is an argument for epoxy on the hull to stiffen the panels, but it should not be necessary for protection.

 

[humbug716]

Thanks for the information. 716 is quite elderly now and I have already had to replace the foredeck as it was a bit of a mess. I know I won't get it perfect but I just wanted to remove some of the worst marks.
With regards to the epoxy I was considering it as a thin base layer and then varnishing on top, I was going to do a discreet small area to test the results.

 

[rob2]

The boat I used to sail on had ply cockpit with varnished seats. We found that it was worth the trouble to apply a single, thin cloth in the epoxy as it increased the strength of the finish and stiopped it cracking. Several coats of varnish followed to protect it from UV and also as a sacrificial layer that can be touched up without marring the overall finish.

Rob.

 

[nedmin]

If the suface is varnished and the stain is in this ,you could try pouring a small amount of methylated spirit on the bad area only and then lighting it with a match,but be careful.When I was in the music business I had a guy who did french polishing and we had a bad stain on a piano top and this is what he did.The stain disappeared like magic.Remember meths flames are hard to see!Dont use too much.

 

[humbug716]

Thanks guys all useful ideas which I can look into.