Erasing blacks marks from under the varnish

[Kenzo]

I am thinking about stripping all the varnish off my boats wooden mast and recoating her from bare wood, this would be an ideal opportunity to erase the blacks marks that show on the wood, I have 2 questions regrding this :-

What causes the wood to go this colour in the 1st place?

&

What is the best way of removing them? Chemical, abrasion etc?

Thanks
BK

 

[tcm]

you need to bleach the wood back. One way i have found to do this is to use the "part 2" of the 2-part teak cleaner from wessex chemicals (google on the web for them) then rinse and dry before any sanding etc.

polls eh, they're rubbish aren't they? Especially er yours....

 

[Peterduck]

If you are located in some part of the world that is not the south-eastern corner of the United Kingdom where the aforementioned cleaner is available, try Oxalic Acid. I have found that several applications may be necessary. Beauty may be only skin-deep, but ugliness [and black stains are the essence of ugliness] goes right to the bone! I suspect that there may be more than one cause of black staining of timber.
Peter.

 

[cliff]

Black marks are caused by either mould or chemical reaction between say Tannic acid in the wood and contamination of the wood before varnishing. Usually it is mould (mildew).

Bleach will remove mould staining after you have removed the varnish. Try a specialist paint / interior decorating shop or a local hardware shop if you have one - I buy concentrated bleach from my local hardware shop by the gallon.
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