Replies

1. 
   mikeinohio | Jul 22, 2021 04:18pm | #1

   I have successfully used Oxalic Acid to remove a few black water stains from oak but I've never used it on such a large scale as you require. Still, it might be something to consider.

   Mike

2. 
   pantalones868 | Jul 22, 2021 05:17pm | #2

   What type of wood? The best thing I've found for removing water marks and stains on wood is Murpheys oil soap in warm water and using a white terry towel rag rub like hell!

3. 
   john_c2 | Jul 22, 2021 06:09pm | #3

   Oxalic acid is the best wood bleach I've used.

1. 
   Badger1805 | Jan 17, 2022 06:48pm | #4

   John, have you ever had success removing black condensation stains with oxalic acid? I haven't had much success thus far with either bleach or oxalic acid, but if you have, perhaps you can shed some light on how you did it.

4. 
   pantalones868 | Jan 18, 2022 02:59am | #5

   Oxiclean( hydrogen bleach) will take care of the mildew, thats mostly what that black is -scrub with a tooth brush and it will remove a lot of the black staining as well. Then try the afore mentioned Murpheys Oil Soap, hot water and a terrycloth rag. That will do a lot to remove tannin bleed. Chlorine bleach is pretty destructive to wood and you need to neutralize it. I've used oxalic acid to lighten wood, it's a long process and kind of nasty stuff and I haven't found it to be that effective at removing stains. Excellent brush cleaner though. I made all my windows, they're redwood and single pane glass. I get a fair bit of condensation so I get water sitting on the bottom of the sash. The water rolls down the glass and gets between the glass and the sash or mullion and then underneath the finish. You try to seal that but the glass and the wood move at different rates and any sealing you do gets compromised. Cleaning and touching up is an annual event.