Black water marks on Alpine Ash

[henlan77]

Hi all,

I am building a house and have installed beautiful alpine ash windows and door jambs.

Unfortunately some of the ash has become wet during the build, through storms and careless tradies:((.

The ash has developed black spots and streaks where it was wet. It is not on the surface (ie it is in the grain) and looks like it could be a mould or something. However it is a cold dry climate (snowy mountains NSW) not the tropics.

Any ideas of what the black spots are and how to remove them prior to oiling the ash? I don't want to risk bleaching the wood with harsh chemicals.

Thanks in advance.

[henlan77]

I have done some more research and have found that oxalic acid may do the job. I understand this is also used to clean decks etc.

Does anyone know how harsh this treatment might be to new interior timber?

Any help appreciated.

[jimbur]

The following comes from a book called Repaing and Restoring Antique Furniture by John Rodd.
it come under the heading of bleaching:
A saturated solution of oxalic acid was always recommended in old books and is very effective in taking out some ink stains, iron stains from oak etc. in short it may be tried and will sometimes work. Before polishing the acid should be killed by the application of an alkali such as a weak solution of washing soda.

Hope this helps. Best try it on an offcut first.
Good luck,
Jim

[Chipman]

People do use oxalic acid, especially on antique furniture etc... if you do decide to use it... remember it is a dangerous chemical and you will need to take appropriate safety precautions.

See this MSDS

http://www.jtbaker.com/msds/englishhtml/o6044.htm

I tried it on some silky oak... it helped to remove some of the black water/rust stains but not all of them

Chipman

[journeyman Mick]

Oxalic will remove a lot/most/all the stains but also requires copious amounts of water to wash it off, otherwise you'll get a horrible yellow stain. You could try some of the commercial deckwash solutions which contain oxalic as well as detergents to remove stains.

Mick