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How to prevent mold on rough-turned madrone?

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Feb 16, 2012
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The title says it all. I've had a hell of a time with mold spots on roughed madrone bowls. This happens after boiling the wood, while the pieces are air-drying. In the space of about 24 hours the bowls go from flawlessly clean wood to being riddled with spots that go all the way through. In my last batch I did try a few different things which suggest a future experiment. I pressure-cooked one bowl (15 psi for 90 minutes) and boiled the rest (2 hrs of full boil). The pressure cooked bowl surface-dried much faster, has a lighter color and got less mold. Of the boiled bowls I left one unsealed and coated the rest with Anchor-seal. The uncoated bowl has substantially less mold. Next time around I'm planning on a bleach dip after boiling, no sealer and and air drying in full sun. Anything else you all can suggest?

Kalia in Sebastopol, CA
 
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I have never sealed boiled madrone - pull from the pot, stack on edge until cool - generally next morning. When surface dry and cool, stack rim down with plenty of air flow for a few days, then on wire shelves to dry. Works for me - no mold.
 
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Kalia, I had similar experiences with local woods here. A friend of mine came up with a simple and cheap but effective solution(!): One (weight) part citric acid (C6 H8 O7) to five parts warm water, stirred, cooled and applied to the fresh cut surface.
Very little bleaching effect and the mold doesn't even start.
 
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Kalia, I had similar experiences with local woods here. A friend of mine came up with a simple and cheap but effective solution(!): One (weight) part citric acid (C6 H8 O7) to five parts warm water, stirred, cooled and applied to the fresh cut surface.
Very little bleaching effect and the mold doesn't even start.

Thanks for this tip! I'm going to try this to preserve white color in the sap wood of walnut and cherry bowls. It's hard to keep it from turning gray, especially if the tree was cut while actively growing (vs during dormant season). I wonder if citric acid treatment could help keep holly white while drying which I understand is also challenging.
 
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I would think that Oxalic Acid would be prefered to either vinegar (Acetic Acid) or Citric acid for preserving the white color of sap wood. In order for any acid to be effective in controlling the growth of fungi, the water solution must be fairly acidic. Fungi grow best in a mildly acidic environment.

When your blanks come out of the boiling water after two hours, they are essentially steril. If you allow the water to evaporate from the surface of the hot blanks, you will probably not see any mold growth. I suspect that your Anchorseal is contaminated and is the source of the fungal growth.
 

Dennis J Gooding

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The title says it all. I've had a hell of a time with mold spots on roughed madrone bowls. This happens after boiling the wood, while the pieces are air-drying. In the space of about 24 hours the bowls go from flawlessly clean wood to being riddled with spots that go all the way through. In my last batch I did try a few different things which suggest a future experiment. I pressure-cooked one bowl (15 psi for 90 minutes) and boiled the rest (2 hrs of full boil). The pressure cooked bowl surface-dried much faster, has a lighter color and got less mold. Of the boiled bowls I left one unsealed and coated the rest with Anchor-seal. The uncoated bowl has substantially less mold. Next time around I'm planning on a bleach dip after boiling, no sealer and and air drying in full sun. Anything else you all can suggest?

Kalia in Sebastopol, CA

it may be a matter of the local climate, but I find that boiled madrone is far more susceptible to mold if it is bagged rather than left uncovered to dry.
 
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Well, I once turn my madrone and have never had mold problems. Not positive on the boiled method. One thing I didn't like about boiling, is that it tends to muddle the colors together. I would never put madrone in direct sun light for drying. I would keep them inside, and I start mine out on the concrete floor for a day or two, then up on a wire shelf. They need air circulation, but I would not put a fan on them. I have used lemon juice on mine to remove metal stains from the chuck. If I do it when the blanks are more dry, the lemon juice can leave bleached out stains. Not sure what the other mold killers would do.

robo hippy
 
Joined
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I have never sealed boiled madrone - pull from the pot, stack on edge until cool - generally next morning. When surface dry and cool, stack rim down with plenty of air flow for a few days, then on wire shelves to dry. Works for me - no mold.

My first time working with boiled madrone I set them to air dry in cool shade (with no sealer) but they molded really badly. Maybe not enough air flow...
 
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The citric acid solution sounds interesting. Any reason that would be better than a bleach solution? These are rough-turned, so if the bleach affects the surface color it doesn't matter.
 
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Sebastopol huh.....i spent some of my hippie days on the Russian river.That was a good time...in 66" its all changed now tho. ...

I am now in Madrona country and it is cooler here so i have cut
and turned a bit of Madrona.....but never seen mold on it...
Got to be the weather diff between Sonoma county and Washington
state where i am.....

Sorry Iam really no help here with your prob good luck
 
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Bozeman, MT
Paul Gilbert's comment got me thinking biologically rather than as a woodworker. If you're seeing such a severe mold problem and others in relatively similar climates have not, I wonder if there is a reservoir of mold spores in your shop. There has been some fairly overanxious talk online regarding environmental mold and I am not suggesting you be alarmed. Rather, consider the temperature and humidity and air movement in your shop.
  • If there is visible mold in nooks and crannies in the shop, you could wipe/spray with a fungicide (dilute bleach works).
  • It's possible to measure the humidity in an environment, though I have no idea how accurate affordable humidistats might be. Maybe you would benefit from a dehumidifier to reduce the mold-encouraging moisture.
  • Is your house/shop very tightly sealed? You could do a 'blower test', which is something HVAC people do often, to find out your rate of air changes, or just open doors and windows during the dry season or at least on a dry, breezy day. Repeat regularly.
  • In your photo, I see clear plastic curtains--could they be creating a 'plastic bag' effect?
  • If you've got plastic curtains, as I do, you are probably turning a good amount of wet wood. Maybe those are the days you need to open the windows/doors.
  • You local county extension agent could help you learn what mold species you're growing and what temperature it likes best.
Just thinking out loud about possible causes. Good luck.
 
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I forgot to mention, that I use the citric acid solution (in that concentration) before applying Anchor Seal. Before, I had had a few cases of mold *under* the Anchor Seal. Very annoying! Guess Paul G is right, maybe contamination of the AS added the problem.
 
Joined
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Paul Gilbert's comment got me thinking biologically rather than as a woodworker. If you're seeing such a severe mold problem and others in relatively similar climates have not, I wonder if there is a reservoir of mold spores in your shop.

-- This is something I've been wondering about as well. My shop is a converted garage with good (sometimes excessive) airflow. Our area isn't particularly humid, though when I processed the madrone we had been getting some much-needed rain so the ground was moist. Late last year I had a massive mold event with a batch of rough-turned albizia (silk tree) bowls. They were unsealed and the weather was cool. They could very well have left a reservoir of spores in the shop. Oddly, the first time I had mold on madrone it happened in a brand-new shed that had never even gotten rained on.
  • If there is visible mold in nooks and crannies in the shop, you could wipe/spray with a fungicide (dilute bleach works).
I've never had free-range mold in the shop. Only on roughed bowls or things stored in plastic.
  • In your photo, I see clear plastic curtains--could they be creating a 'plastic bag' effect?
The shower curtains are only around the lathe, to keep my entire shop from being hip-deep in shavings when I rough-turn. They get pulled aside or taken down when I'm not roughing.
  • If you've got plastic curtains, as I do, you are probably turning a good amount of wet wood. Maybe those are the days you need to open the windows/doors.
Fair point.
  • You local county extension agent could help you learn what mold species you're growing and what temperature it likes best.
Temperature regulation is tricky in my space. I think figuring out a place where I can set at-risk bowls to dry with maximal air flow is my best bet. My husband has offered a day of his time to help with a gigantic shop cleanout as well, which might help. I need to work my way through some of the logjam first, but then it's shovel time!

Good suggestions. thank you.
Kalia
Just thinking out loud about possible causes. Good luck.
 
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