How to remove water stains from Oak

[Doug Carpenter]

Help?

I am repainting an old 3 panel Pella sliding door. I am going to refinish the sill as well. It is oak and has some black stains from water. I have stripped it of any finish that was present but it was so dry I think the last time it had a finish on was when it was installed in the fifties!

Can anyone suggest a way to remove or lighten the dark stains?

[Tony Bilello]

Mis some oxalic acid with water and form a heavy paste. Paint this paste thickly over the black rings. Place a slightly wet rag on top and put a very warm clothes iron on the rag for a minute or so then do it again. Remove the oxalic acid and see how well you did. If you still have ring, mix up a new batch of oxalic acid and repeat. This time get a little braver and raise the heat of the iron.
When you have removed 90% of the ring, the rest should come out with a light sanding.

[Doug Carpenter]

Thanks, I'll give it a try.

[phil harold]

+1 on the Oxalic Acid

[Tony Bilello]

Actually, the black stains on oak are usually from contact with some form of iron.The iron reacts with the tanic acid in the oak when wet and creates a black dye. The source of the metal was probably an old can.
Whatever the cause, the Oxalic will remove it.

[Howard Acheson]

Originally Posted by Tony Bilello

Actually, the black stains on oak are usually from contact with some form of iron.The iron reacts with the tanic acid in the oak when wet and creates a black dye. The source of the metal was probably an old can.
Whatever the cause, the Oxalic will remove it.

The tap water in many places contains enough iron oxide to react with the tannic acid in oak.