Mildew in wood

[Don McClure]

I often have difficultu with mildew occuring in the sood that I have freshly cut, prepared for bowl blanks and put Anchor Seal on. The pictures show walnut that is onlly 30 days old! Any way to prevent this?230062

[Jason Ritchie]

I'm not sure how to correct this but I have read where a few others have had the very same issue using anchor seal. I wonder if wiping it down with denatured alcohol before applying anchor seal would kill the mildew? Do you store your wood outside after you seal it? I have been storing mine inside and have no such issues but I just built a wood shed to store my wood to get it out of the shop so I may run into this at some point.

[Faust M. Ruggiero]

Don,
Fresh cut walnut and box elder as well as maple mold quickly in our area. Don't use anchor seal on your rough outs. Bag them and change the bags daily until the wood begins to dry. Also, don't store them in too moist an area. Once mildew grows, you can use bleach to cut it back but you can almost count on wood discoloration. Another way to help the problem is to let your logs dry several months prior to processing them especially if you are using wood cut while the sap is still running.

[Dale Miner]

What you show in the picture of the walnut is not mold. That is the juglones in the wood causing the sapwood to change color. This is one of the processes that causes the heartwood to have it's color. The only way to prevent the sapwood from discoloring in walnut it to get the sapwood dry before the change occurs. In cold weather, there is a natural slowing of the change. In warm weather, a week or two is enough for the degrade.

The bluish grey discoloration of maple, ash, and box elder is a result of a fungal growth. When the temperature is below about 40 degrees, the fungus is slowed or inactive. Warm temperatures speed the fungal activity. A washdown with household bleach will kill the spores on the surface, but once the chlorine leaves, the wood will be repopulated with airborne spores and the fungus will flourish as long as there is sufficient moisture present. Washing the blanks, and especially rough outs with a boric acid solution will kill the spores on the wood, and when the water of the solution evaporates, will leave the boric acid on the wood, making the surface of the wood toxic to any air borne spores. If the wood has already been attacked by the fungus, there will be fungus in the wood that most surface treatments will not have much effect on, and the fungus will continue to grow as long as the moisture content of the wood allows it. Bleaching the wood to remove the stains will generally have little effect.

I submitted a write-up to the AAW magazine in the Tips and Tricks section regarding boric acid and mold a year or so ago.

When you anchorseal a blank, applying anchorseal to the sides of the blank, and not to the top and bottom helps. Coating the entire blank slows moisture loss to the point that any fungus that is present is almost assured a safe haven.

The best bet to prevent degrade of the wood is to turn as soon as possible after the tree is felled, and dry the roughouts as fast as possible without experiencing cracking.

[Dennis Ford]

A friend uses a Borax/water solution on his wood before sealing to prevent mold. I have been meaning to try that but most of the time I am trying to encourage spalting, not prevent it.

[Don McClure]

Thanks for all the suggestions. When I usually come upon a downed tree to process, I will cut it into logs, split and anchor seal it. Then I have stored it inside, and even outside in sheds with the problems of mold occurring in most of our common woods such as pecan, maple, magnolioa, poplar, sycamore and especially the walnut pictured. It has been frustrating. I plan to try the boric acid wash next. Any other thoughts will be appreciated. By the way, some of thje walnut I did only coat the ends of the log with Anchor seal and not the flat surfaces just top see how it would do. I live in upper Souith Carolina which does have humid summers.

[Bernie Weishapl]

Don when I cut my logs in half I only anchorseal the ends and about 1" or 2" over the edge. I have never had a mildew problem. Of course in Kansas we generally don't have much humidity either so that could be a factor. When I first started I coated the whole half log except the bark and did get mold. On roughed out bowls I do coat the whole bowl. I keep them in a cold room around 60 to 65 degrees and humidity of 45% to 55%. Have had one out of 70 crack and no mold/mildew. Takes about 8 months to a year to dry. I then bring them into the shop for a couple of weeks before hitting the lathe.