On 26/07/2012 10:52, Chris Hogg wrote:
On Wed, 25 Jul 2012 22:00:09 +0100, Eddy
wrote:

Pete C wrote:
Pee on the floor?

Human urine? Are you serious? If you are, I'd definitely try it.

That is urea for the most part. The trick I recall requires ammonia.

Chris Hogg, the accidental staining is against the grain, and across
several planks, rather than with the planks, so one would have to
blacken the whole floor to hide the streaks. Anyway, we want our nice
oak floor back!

Martin Brown, thanks for the warning to mop up well after using lemon
juice. Will try the juice tomorrow. Thanks for the rhubarb leaves tip.

Yes, there should be a clear warning on the sides of packs of iron
sulphate.

Thanks people.

Eddy.

Another suggestion if you're desperate: a combination of hydrogen
peroxide and phosphoric acid in sequence. Reasoning: ferric phosphate
is colourless (white in powder form), but the 'iron sulphate' sold
commercially for garden use is usually a mixture of ferrous and ferric
iron sulphates, so there may well be some ferrous iron still present
in the wood on your floor. The addition of hydrogen peroxide should
oxidise any remaining ferrous iron to the ferric state, and the
phosphoric acid will then bleach it. If you use the phosphoric acid
alone without pre-oxidation, you may get a mixture of ferrous and
ferric phosphates, which is black.

Hydrogen peroxide is available at most high-street chemists, and IIRC
the chemical used for lowering the pH of fish ponds contaminated by
fresh cement is phosphoric acid, and can be obtained in aquarium
shops. Use them in sequence rather than as a mixture. I make no
guarantees though, either that it'll work or that it won't spoil the
surface of your floor. Personally, I think I'd try sandpaper and a
re-varnish first!

Definitely try all of these suggested recipes on a piece of scrap oak
that you have made a controlled iron stain on and leave for a couple of
weeks to see if there are any bad side effects.

You might also want to try looking in the library for a book called
"Henleys 1001 Formulas and Trade Secrets" under cleaning iron stains -
but take what they say with a big pinch of salt and ignore anything
involving mercury or conc. acids!

--
Regards,
Martin Brown