Letting varnished wood go mouldy

[Avocet]

My boat is laid up (and will be for some considerable time)! I was about to wipe some slime / dirt off one of the locker covers (varnished wood) today, when I had the thought that as ultraviolet seems to be the main killer of varnish, perhaps I should leave the growth there to block out some light?

Does this sound daft and/or a lazy man's excuse for not cleaning the boat - or might it be useful to leave the stuff until ready for re-commissioning?

 

[TheBoatman]

Sorry but that thinking doesn't add up. Your problem will be that the growth "stains" the timber and is a bugger to get cleaned when you decide to re-varnish ~ you'll have loads of greenish/blackish patches that will always show through the new varnish.
IMHO take some time and re-varnish it now and then cover the boat up with a cheap tarp.
It could save you loads of time and effort in the future.

Peter.

 

[Avocet]

Ta Peter. I should maybe explain a bit more though. It's just been varnished this summer so it's not the case that the growth can get to the wood - there are no scratches in it (yet!) The "mould" is a mixture of tree sap and that sort of thin green/black "slime" that wipes off very easily (at this stage anyway!) with a wet rag. I know what you mean about the wood going black but that isn't quite the same situation as I have here.

I have to say the more I think about it, the dafter it sounds but if I have the varnish out any time soon, I might try and make a couple of little "test pieces" and leave them out - one dirty, one clean just to see if it makes a difference!