Q. How dry do we need to get wood so that it will not get mold or mildew on it? I am thinking of oak and hickory.

A. Mold and mildew are fungal caused. In order to be active, a fungus needs warm temperatures (80 to 100F is ideal); oxygen; food (for mold and mildew, they survive mainly on microorganisms in the air, dirt, dust, and so on; there is very little inside the wood that they like to eat, so they stay on the surface); and moisture. The fungi do essentially need liquid water, so this means that the wood moisture content must be somewhat higher than 22 percent MC, with 35 percent MC and higher being better.

Under 22 percent MC will not provide the needed moisture, but if dew forms at night, or there is a water sprinkler, or rain, or frequent wetting from other activities, such as mopping or wet rag wiping, the surface moisture can be temporarily be high enough (even though the average for the piece is under 22 percent MC) to support fungal growth for a short while until it dries out again.