Oxalic acid

[pandos]

No it seemed to bleach the 2 pack paint on my hull with lines from the drips off the acid.

..I have used it above single pack paints with no issues...I usually mix mine with as concentrated a solution as I can using water at about 50 degrees C.

Maybe you have managed to make/ get a more concentrated version or perhaps there is a different cause, certainly something to beware of...

 

[zoidberg]

Speaking of oxalic acid, I noticed today that Lidl Stores locally are seling 1 litre bottle of 'Wood Cleaner' - which is essentially oxalic acid - for £4.99.
I dunno what concentration, orif it's any good for boaty-wood, but it seems worth a try.

That'll save me harvesting all Milady's 'barb and boiling down all the green leaves....

 

[Daverw]

we buy the crystals off eBay £18.99 for 2.5 kg makes loads of paste, we on the Humber use it all the time, the mud here is quite sticky and mud berths don’t help either, never had an issue with staining