Black marks on oak

Just a guess, but they may be tiny pieces of the steel wool embedded in the oak that have oxidized with the combination of water and tanic acid from the oak.

Roger Redford asks:

Good luck getting them off. Those are caused by a reaction between the tannin in the oak--tannic acid--and the steel wool. Using anything steel on oak is a mistake, and hosing it down afterwards intensifies the mistake.

Individual stain bleaching might work. An awful lot of work, though. Use oxalic acid, rubber gloves and goggles and try on a small piece.

Charlie Self "The test and the use of man's education is that he finds pleasure in the exercise of his mind." Jacques Barzun

You used a hose to spray it off....mildew perhaps?

Or maybe bug droppings? I get the latter all the time on tools and projects in my shop. Look like clusters of pinhead sized ink marks.

-- Cheers! Duke

Where is your shop??!! It was a joke, wasn't it!!??

Most likely those are stains cused by reaction of tannins in oak, water and left over particles of steel wool. Steel wool anywhere around bare wood is a generally bad idea

Across the driveway from my house.

Sadly, no. But when you live next to 500 acres of pastures with cows grazing in them, you're bound to have a few flies around. Good ole fashioned fly paper does a pretty good job on them.

-- Cheers! Duke

Steel wool - bad idea on oak, especially with water.

Oxalic acid bleach should shift much of it. Don't waste your time on other bleaches like hypochlorites or hydrogen peroxides (and that includes "wood bleach")

You can probably find oxalic acid as "Barkeeper's Friend", a white powder sold in hardware stores and even supermarkets. You might also find it as one ingredient in some patio deck cleaners. Be warned, the stuff is somewhat toxic - wear gloves and watch out for the dust.

You missed April fools day by quite a margin there but still, it's interesting to see how many fall for it.

Next time try not to be so obviously heavy handed with the stupidity. It'll work better.

"Mike G" wrote in news: snipped-for-privacy@comcast.com:

Whats worse is the bad advice he got. True it is oxidized metal from the steel wool. All he needs is a scraper and they come right up. Leave the chemicals alone. I've had extensive issues after filing my scraper on a bare floor and then grain popping. All those fillings...Beyond that, a scraper is your friend.

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Such as what part in particular ?

No it isn't. It's a complex of iron tannates, not just iron oxides. Rust stains (on many other timbers) are brownish, maybe blackish. The deep black or blueish stuff like this occurs when you have this problem on a tannin-rich wood. The pigment here is that of "iron gall ink" - I've seen manuscripts written with this stuff that are over a thousand years old and still dark.

As to the depth, then you might get away with it - always worth a try. However I recall a hosepipe was involved and in a surplus of water, then these stains can go pretty deep.

It is an oxidation reaction in the chemical sense, which is why oxalic acid reduces the tannate to near-colorlessness.

I daresay, as well, that fragments of steel wool don't have enough ferrous material available to penetrate very deep before being completely oxidized.

True enough, but I doubt that MH appreciates the difference anyway.

What is clear is that it's not merely "iron oxides" that we're dealing with, even if they are "oxidised iron".

Well, here is the secret.

I looked for some oxalic acid. It was hard to find, but I finally found it in product used for cleaning decks: Behr Wood cleaner brightener conditioner

It did the trick. Actually, quite quickly. And that was diluted. I also used a scotch bright this time.

As for the idiot who thought I was stupid, I was just following the directions of the paint remover. It said to use steel wool, and so I did. It gave no warning about possible black marks. Warning: Even more idiots are behind those products you buy.