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Thread: Black on milled oak that's been stored outside

  1. #1
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    Black on milled oak that's been stored outside

    I was given a lot of already milled oak, it's 3/4" thick. That's the good news. The bad news is that it was stored outside under a tarp for a couple of years with some of it stickered, and a lot of it turned black or have lots of black areas. I'm guessing it was due to water leakage. If I try to run these through my planer to clean off the black, then they will be less than 3/4". The black does not look like mold. Is the black "tannin" (I think that's the word) that has come out of the wood? Is there a chemical that might take off the black? Randy

  2. #2
    Does sanding remove the black?

  3. #3
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    A pressure washer will get it right off. My pressure washer is 2500 psi at 4.4gpm. The gpm is not as important as the pressure. More than 2500 will erode the wood. I use a 40 degree nozzle, as one narrower than that will cut into the wood.

    I have White Oak siding on our house, and barn, that I built in 1980. I pressure wash it about every 10 years or so. It turns a silver gray and that stays for 8 or 9 years. The black is probably mold, and mildew, but it comes right off.

    I just use water. Bleach, and detergents can cause other problems, and I've found no difference in how long it stays clean.

    This White Oak siding was pressure washed a day or so before I took this picture. It was starting to get black.
    Attached Images Attached Images

  4. #4
    If it's tannin stain, mildew or mold Oxiclean will get it off.
    WoodsShop

  5. #5
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    White oak siding...is that even legal? Talk about sacrilege...I can't imagine being so flush with WO that I used if for siding...definitely a first-world problem!

  6. #6
    I agree that it is probably a reactive stain, not mold. You may be able to bleach this with deck cleaner. Sometimes it runs deeper. You can always ebonize it and go with the black.

  7. #7
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    Quote Originally Posted by Prashun Patel View Post
    I agree that it is probably a reactive stain, not mold. You may be able to bleach this with deck cleaner. Sometimes it runs deeper. You can always ebonize it and go with the black.
    Ok, just did some googling for deck cleaner (thanks for idea!) and ended up reading about oxalic acid as that's seems to be the predominent ingredent in deck cleaner. I found many references to it cleaning off tannin stains (along with a long list of others). Think I'll buy a lb or two, mix with water and see how it works. At least I'm pointed in a direction now.... Randy PS Anybody out there used this for wood cleaning?

  8. #8
    Oxiclean does almost as good as oxalic with tannin stains, and it's a lot safer to use, might give that a try.
    WoodsShop

  9. #9
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    Quote Originally Posted by Jacob Reverb View Post
    White oak siding...is that even legal? Talk about sacrilege...I can't imagine being so flush with WO that I used if for siding...definitely a first-world problem!
    I paid $100 a thousand for it when I built the house, and barn in 1980. That's 10 cents a board foot. On later spec houses I built here on the lake, I splurged, and bought dressed White Oak, which wasn't much more. Soon after I built the house that siding is on, Senco had stainless nails available here, so no more of that problem.

    As I have built additions onto our house, I've pulled off that top layer, to use as the first layer of Board on Board, so the streaks are no longer seen. That picture is the last section of our house with the original outer layer on it, but that will be used for the next addition.

    This is timber country, and there are multiple mills that sell lumber from what grows around here.

    Seriously, I've dealt with this black stuff on White Oak for 40 years now, and it comes right off with water pressure. If you put a chemical on it, you're still going to have to rinse it off. This is first hand experience, and not just conjecture.
    Last edited by Tom M King; 06-09-2019 at 6:14 PM.

  10. #10
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    Quote Originally Posted by Tom M King View Post
    I paid $100 a thousand for it when I built the house, and barn in 1980. That's 10 cents a board foot.
    I'd say that qualifies for a belated YOU SUCK! award!

    Seriously, nice score. I've bought green white oak from sawmills around here (usually 60˘/BF), but we get these weird tunnels through it (insects? rot? dunno) that are coated with something black, probably the same stuff as on the OP's wood. I asked the sawmill operator about it, and he said, "The further south you go, the poorer the hardwoods get and the better the softwoods get...and vice-versa."

  11. #11
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    Jacob, I guess you missed the whole drama about the “you $uck” phrase. It’s not permitted here, though I know you said it as a compliment.

  12. #12
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    I know the story, and don't mind a bit. I bought it by the semi load, and used it on several houses over several years. The clear, big logs are sold for high dollars as veneer logs, but the rest is just cut up however you want it with no grading.

    The first two houses I built here on the lake had Cedar siding on them. Flying squirrels ended up in both attics. Woodpeckers like it too. They can't do anything with the White Oak. Some of those houses, that I sold back then, have been resold for over a million back when things were crazy.

    The last White Oak I bought, a few years ago for an addition, was .65 a foot for dressed. Green works fine for this vertical, board on board siding.

    We're right where the Coastal Plain starts to turn into Piedmont, and hardwoods are just fine, as are what softwoods grow here. The counties around us are the largest producers of timber in Virginia, and North Carolina. We're right at the border of both. The lake is mostly lined with houses now, but for many miles in all directions behind those, it's mostly all timber land.
    Last edited by Tom M King; 06-09-2019 at 8:12 PM.

  13. #13
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    Quote Originally Posted by Joe Wood View Post
    Oxiclean does almost as good as oxalic with tannin stains, and it's a lot safer to use, might give that a try.
    Joe - As my wife (nor I) have any experience with Oxiclean, is it a liquid or powder, how did you use it? The oxalic acid is a powder you mix and have to keep hot and then triple rinse to get it all off. Just wondering about all the water going on to one of these boards...maybe as it probably wouldn't have enough time to penetrate, might not make them cup/warp/etc. That was also my concern about pressure washing - driving the water into the board. I'd rather try oxiclean first, less hazardous. And, don't own a pressure washer. Randy

  14. #14
    It's a crystal Randall, mix in hot water, spray or brush it on, use a brush to scrub for a couple minutes and rinse it off.
    WoodsShop

  15. #15
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    If this is white oak, it is just the tannin stain, no amount of sanding will remove it. I have some air dried white oak that is as dark as walnut and is solid color all the way thru.

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