Just add a little moisture and it is ready to grow.
The photo above is mold, growing on the drywall in our little storage closet which doesn't have enough ventilation, on a wall that is unusually cold. Drywall is wonderful fungus food, which is one reason why I have always disliked it. I always thought that the mold drifted in the air and grew on damp surfaces, but according to Rob Dunn in his wonderful book, Never Home Alone, it might well be actually baked into the drywall when it is manufactured.
Dunn writes about the work of Danish researcher Birgitte Andersen of the Technical University of Denmark, who looked closely at drywall, doing research that Dunn worries might be difficult in the USA, where "there might be negative consequences to studying what lives in drywall produced by companies that have an enormous stake in maintaining the status quo."Birgitte studied thirteen sheets of drywall from different hardware stores and sterilized their surfaces to ensure that nothing had settled on them. She then soaked the drywall in sterile water.
Finally, one day she saw growth. Then more growth. Birgitte found lurking inside of brand-new drywall the fungus called Neosartorya Hiratsukae. This fungus has recently been implicated in the complex mix of causes of Parkinson's disease. ...Neosartorya Hiratsukae was on every sheet of drywall, regardless of type, regardless of which store it came from, and regardless of which company it was made by.
She also found Chaetomium globosum, an allergen, and...
..there it was, black and potent, Stachybotrys chartarum, on half the samples. Once it started to grow, it covered the drywall discs, darkening them with life. Nor were these the only species present. Eight other kinds of fungi were also found inside the drywall, waiting.
According to Dunn, she found "without a doubt, the fungi in the drywall in homes comes pre-loaded in brand-new drywall."
The same kind of investigation might well find fungi in wood or any other material we can cover our walls with. But drywall is made with cardboard and paper, which might be the hotspot for growth. Also, as we noted in an earlier post, corn or wheat starch is often used as a binder.
The [gypsum] plaster is mixed with fiber (typically paper and/or fiberglass), plasticizer, foaming agent, finely ground gypsum crystal as an accelerator, EDTA, starch or other chelate as a retarder, various additives that may increase mildew and/or fire resistance (fiberglass or vermiculite), wax emulsion or silanes for lower water absorption and water.
Birgitte notes, "It's fine, just don't let drywall get wet."
But as my bit of drywall shows, it doesn't have to get totally wet. It just has to be cool enough to condense a bit of moisture, with boxes piled in front so that there is no ventilation. That's enough to feed the fungi.
Dunn suggests that if you are building a new house, you might avoid drywall, particularly in areas that get wet, because you can't be sure that it doesn't already have that toxic black Stachybotrys chartarum already baked in. I have said the same thing but, as we have noted before, the alternatives are all more expensive. But it might be worth the cost; as Steve Mouzon has written,
They call that boring white stuff we put on our walls "drywall" because so long as you keep it dry, you have a wall. But just as soon as it gets wet, it turns to messy mush. And even if it doesn't fall apart, it loves to host mold and mildew and make your family sick.... . We need to learn how to build durable and resilient buildings like our great-grandparents did so that the summer shower is no reason to call the insurance adjustor; you simply wipe down the walls that got wet and never give it a second thought.
In the meantime, I have figured out why that drywall was so cool; it is on top of my old foundation wall, enclosing an air space that is uninsulated. I am just going to remove it and leave the foundation exposed so that there is no void to get cool enough to condense moisture on the wall. I didn't need it there in the first place.