Bleaching dark water spots from wood

[DavidMcMullan]

I want to revarnish the companionway steps. They are made from oak veneered plywood. Where the varnish has been damaged there are some dark water stains. What is the best way of bleaching these before revarnishing? Is it Oxalic acid or Y20/Boracol or ??
Do you apply it to the stained area only or to the whole step to keep the colour uniform?
Thanks in advance. David.

 

[geem]

Oxalic acid gets rid of black stains on our doors at home

 

[Concerto]

You can also use supermarket own brand thin bleach (it is unscented). Try diluting at 4 to 1, if this does not work, increase the strength progressively until 1 to 1.

Alternatively Liberon make a wood bleach that is supposed to be very good.

 

[longjohnsilver]

Oxalic acid gets rid of black stains on our doors at home

Definitely oxalic acid. Cheap as chips.

 

[VicS]

You can also use supermarket own brand thin bleach (it is unscented). Try diluting at 4 to 1, if this does not work, increase the strength progressively until 1 to 1.

Alternatively Liberon make a wood bleach that is supposed to be very good.

Liberon wood bleacher is an oxalic acid and ethanol solution.

The AG Woodcare website has basic instructions for using oxalic acid. It also mentions using it in an ethanol or methylated spirit solution.

http://www.agwoodcare.co.uk/Item/oxalic_acid