Black Mold on Red Oak - Woodworking Talk - Woodworkers Forum
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post #1 of 5 Old 09-30-2014, 09:32 PM Thread Starter
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Black Mold on Red Oak

Hi Everyone - This is my first post. I am not much of a woodworker but I do have a problem that I could use some help with.

I have made 3 Beer Flight Paddles out of Red Oak and finished them with Tung Oil. After about a year of use I have noticed that 2 of them have been turning black. I am assuming this is Black Mold. I sanded the paddles and was able to get rid of the discoloration on the surface. I read that the mold may be living in the wood and could be killed with distilled vinegar.

I drenched the paddles in vinegar and left them out in the sun to dry. Now the surface of the paddles are covered in black discoloration, worse than before. Is this black mold? Did the vinegar cause the mold to leach out to the surface? Does anyone have recommendations on how I can get rid of the mold/discoloration once and for all?

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post #2 of 5 Old 09-30-2014, 10:27 PM
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Vinegar will turn oak black
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post #3 of 5 Old 09-30-2014, 11:07 PM
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Dr-Rufus, you got some bad advice! Red oak contains tannin that reacts in the form of oxidation when exposed to water, alcohol, iron, sunlight. Vinegar is often used along with old iron nails to make a black stain. These all result in deep black stains penetrating into the grain, particularly summer growth, as you can see.

Lots of finishes are called tung oil, some are, some aren't. Either way, they are pretty terrible at protecting an open grained species, like red oak, from all of the above.

Since those are rather simple to make, toss those and use a finish that will stand up to kitchen use, alcohol, detergents, hot water, abrasion. You will need to build a fairly substantial film of the finish you choose. I use Man-O-War spar varnish for kitchen wood that get's abused. 5 or 6 coats.

Mold is killed by chlorine bleach. Just placing a drop on an inconspicuous area will tell you if it's mold, it will start to disappear.
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post #4 of 5 Old 10-01-2014, 07:27 PM Thread Starter
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Thank You for the responses that helps to clear things up.
I am not ready to throw out the paddles, they were actually more work than I would like to admit.

If these are tannic stains, do you think washing the paddles with Oxalic Acid would help to reduce the discoloration?
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post #5 of 5 Old 10-04-2014, 01:47 PM
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Wood bleach, Oxalic acid can be used but it may not remove all the stain. It also has a tendency to soften oak, leaving the surface like paper making pulp, don't over do it. An alternative might be to remove the existing finish, stain the paddles, then apply a more protective top coat.
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