I live in Goiânia, Goiás! The farm near the center, not even 30km far.

Hey, George! Agaricus needs a casing layer to develop pins,l and this layer  has to be watered sometimes (that’s when I include de calcium carbonate). It also helps to prevent Trichoderma developing in the casing, because the oxalic acid excreted by the mushroom lowers the pH.

I know that in Italy some varieties of Pioppino and Eryngui (Cardoncello) also use casing. But for the majority of the specialties, maybe adding some calcium or just controlling the pH in the water that is used for humidity maintenance can be useful.

In the end air circulation will make most of the difference preventing blotch, that is almost dogma to me 🙃