Q: I am a high-school student doing a science project on how to prevent mold growing on wood. I do realize that this is a factor that many people are very concerned about in their homes.
Do you guys have any suggestions on how I could set up this project or what type of mold resistors I should use? I did some research and found a product called Anti-Growth. Should I use that product in my project or something else? I would be very happy to know some of your ideas for my project. Thank you.
A: We’re flattered that you thought of us when trying to figure out what to do with your science project. We can remember puzzling over the how-tos and the whys of high-school assignments years ago.
Before beginning your experiment, we think it would be helpful for you to understand something about mold, how it grows and what it needs in order to proliferate.
We recall when one of the nightly news programs did a segment on mold infestation in homes flooded by Hurricane Katrina. As the floodwaters receded in New Orleans, mold crept up the interior walls of flooded homes.
One clip showed a house where mold had grown about a foot and half from the floor up a wall. The contractor being interviewed noted that if allowed to go unchecked the mold would creep to the ceiling by the end of the week.
This news clip illustrates the key thing mold needs to flourish — moisture.
The most important thing to consider in controlling mold on wood or any other surface is to remove the source of the moisture it needs to live. If mold is present in a home, look for the source of moisture and eliminate it.
According to literature provided by the Western Wood Products Association, mold growth cannot be supported on wood that is dried to below 20 percent moisture content. Lumber used in residential building, including framing that has been in place for a while during construction, has a moisture content of below 20 percent and won’t support active mold growth.
Green lumber used in framing contains more than 20 percent moisture initially, but between the time the walls are framed and the framing is covered, the studs will have had enough exposure to air to reduce their moisture content below 20 percent. In homes, mold can nearly always be attributed to moisture infiltration of some kind.
Mold can develop if there is a moisture source such as a leaky pipe or dripping gutter. Moisture content can be increased and mold can grow. Once the moisture source is eliminated, cleanup of small infestations is easy.
The U.S. Environmental Protection Agency recommends using a mild detergent and water for most mold cleanup. The Centers for Disease Control recommends a chlorine bleach solution of one part bleach to 10 parts water. The Wood Handbook published by the U.S. Forest Products Laboratory recommends a 2-to-1 water-to-bleach solution.
If you use bleach in any strength to clean mold, make sure the area is well ventilated, wear gloves and do not — we repeat, do not — mix the bleach solution with cleansers containing ammonia. The gas formed is toxic.
Now as to your science demonstration. We suggest you consider setting up a three-part experiment. In three enclosed environments — a cube of clear plastic perhaps — place a wet piece of lumber, a dry piece of lumber and a wet piece of lumber treated with the Anti-Growth product you mention.
You’ll need a moisture meter to measure the moisture content of each piece of wood. We assume that your teacher can help you introduce mold spores into the enclosed areas.
Keep the wet piece and the treated piece in moist environments (more than 20 percent moisture content in the wood). Keep the dry piece at less than 20 percent moisture content (you may have to let air into the enclosure).
We suspect the wet lumber will grow mold and the treated piece and dry piece will not. If this is the case, you will have proved that expensive chemical treatment is not necessary to control mold, rather that by controlling the moisture in the environment you can control the mold.
Good luck on your project, and let us know how it turns out.