Q: I own a company in Michigan that makes outdoor furniture. This past summer I made some furniture items out of cypress. We random sample the moisture and found 8 percent to 10 percent at the time of manufacturing. The material was stored in a heated building with no humidity control after we made it. We did not finish the items. This last December I delivered the items to a customer. Late this spring when the home owner wanted to the finish the items, it was evident that a serious mold problem existed in some pieces. Can you explain?

A: In order for mold to grow you need four elements....warmth, oxygen, water (liquid water is best, which is above 25 percent MC) and food. This decking obviously got wet and had the food that mold like (dirt, dust, micro-organisms, sugar in the sap) available. If you look closely, you will find that the fungus is growing on the sapwood.

 

Sapwood has more food than heartwood. In fact, it is possible that the sapwood had much more sugar that attracted the micro-organisms. It is also possible that what you are seeing is not mold fungus, but another fungus that likes growing on wood. Was this second growth cypress?  If so, it is much more favorable to fungal growth than the old stuff, called virgin growth.

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