black marks from reaction to iron

[phil]

I've been working on restoring my old wooden floors and have been reading up on the subject of some black marks that won't sand out. I thought I would pass it on as this effect may also be apparent in wood radio case restoration.

what happens is that when wood is in the presence of iron ( floor nails in this case) a reaction happens over time between the tannins in the wood and the iron from the nail. the result of the reaction is that the wood takes on a black mark which bleeds through the wood in the direction of the grain. I have seen this effect before in radios, but always chalked it up to being a rust stain. well what I have learned is that rust stains are brown not black and blackening of the wood is the result of this reaction.
I am seeing this effect in fir. I know it also affects oak. I am unsure of the degree in which walnut and other radio cabinet woods are affected. Often the wood which is near the nail and severely affected is softened as well. The marks are not nearly as apparent in sanded wood as they are when the wood is wet or finished with a topcoat.

To fix, or should I say hide, the issue I have bought a chemical called Oxalic acid. It is available from Mohawk finishing supplies and comes in either a 16 ounce bottle, which makes 2 litres, or a 4 litre paint can of crystals. The crystals are then dissolved in hot water for application. On the can it says to mix it up, brush it on and let dry overnight. some instructions I have found also suggest neutralizing it with baking soda afterward. - probably a good idea.

I have yet to try it but thought I would pass on the tip anyway and I'll report back if I find i have any disastrous results. It is poisonous so care in handling it must be observed. If you use it , try some samples and bear in mind that it may remove some of the patina that you would perhaps rather keep. I just thought I'd write in about it because I never knew about it and it might help, perhaps with some unsightly marks which deter from the appearance of some sets that have had particularly bad storage.


Phil

[phil]

I know it is off topic but I applied the oxalic acid to my floor last night. I had sanded about the thickness of a Loonie off the floor and the marks were way down in the wood and appeared like black stains near every nail and in some random places. The floor looked dirty.
I put it on all over and went back just after it was drying and painted the floor one more time with hot water.
the result is that it removed all the black marks and it lightened the floor somewhat It looks much better and I am pleased. It is sort of a "patina remover" . I wouldn't recommend using it as a matter of course, but it sure changed the look of things and for the kitchen looks much nicer than a dirty looking floor. I think it would be helpful on a wood radio case where some part was not matching in color to the rest.
Phil

[kuzzy]

Phil,

Where do you get your Mohawk products from?

Paul

[phil]

http://www.mohawk-finishing.com/dist_lookup.asp

if you scroll to the bottom , there are two distributors listed in Ontario (Richelieu)
Canada Richelieu Ottawa, ON 613-737-6571
Canada Richelieu Mississauga, ON 905-672-1500

I use Mohawk western finishing supplies here in Vancouver.

The Oxalic acid worked well on these black marks. It took most of them away and lightened the floor slightly.
I then did two coats of clear danish oil, then a couple more with some pigment and some terpentine in the mix, i applied that with sandpaper. I was able to slowly bring the color back up where I wanted. I followed that with three coats of clear polyurathane, and I am about to do hopefully the final coat using semi gloss poly. This turned out to be a LOT of work, but should last decades like that. The oil toughens the floor and brings up the color of the wood, and the poly creates a tough protective shell. this seems to work well with Fir, as it is quite hard wearing but a softer than a lot of the hardwoods.
Laminate would be so much easier, but in this case I really wanted to see the original woodwork. I liked the look with just the oil , but it didn't seem that would be practical for a kitchen floor.

Phil

[radionut]

Hi Phil
Would you be able to show a picture of the floor. sounds like you went to a lot of work.My mums house has two floors that are tongue and grove ,that needs doing badly. This sounds like I should try .
Bruce

[phil]

you can read the whole story on my floors here Bruce.

http://www.oldhouseweb.com/forums/viewt ... &sk=t&sd=a

Phil