Spots of green ambergrease appearing through my anti fouling. Any ideas?

[Bertramdriver]

The boat is old, 1980, but has shown no tendency to osmosis blisters. She stands 7-8 months stored ashore so the hull is dry. Unfortunately she's not so dry inside with water in the bilges most of the time.
I've just noticed that green amber grease spots are appearing on the hull next to the genny. Not a massive problem but perplexing. Any ideas?

 

[sarabande]

It is not ambergris, which is a solid, waxy, flammable substance of a dull grey or blackish colour produced in the digestive system of sperm whales.

Are they acidic ? Have you used a copper-based antifouling ?

 

[Bertramdriver]

It is not ambergris, which is a solid, waxy, flammable substance of a dull grey or blackish colour produced in the digestive system of sperm whales.

Are they acidic ? Have you used a copper-based antifouling ?

Yes to both and it seems to have a crystalline formation.

 

[sarabande]

I forget which tends to migrate more: fresh to salt, or salt to fresh.

It sounds as if there might be a precursor form of osmosis: water coming out of the hull and picking up the copper in the antifouling, then forming copper / copper sulphate crystals under a layer of paint.

Is it worth doing some photos and putting them here ?

 

[enterprise]

Think you were thinking verdigris ?, if it's ambergris, sell it as it's worth a fortune to the cosmetic industry!

 

[Bertramdriver]

Had a look and a poke around and fear I may have a stress fracture in the hull which is allowing fresh water to migrate out behind the anti foul and force it's way through. Trouble is I want to leave the yard next week and I've got 170 miles to go, so it'll be stress all the way. I'll get the new yard to have a good dig at it at the end of the month.