A. Organic adhesion
Organics mainly come from the following aspects:
a. Food residue floating in the air, corpses of insects, etc.
b. Organic components in stone glue
c. Stone surface decoration, such as wood, cardboard, etc.
d. Near the accumulation of stone
B. Wet
There’s nothing more to say, the air is damp, wet stone, water leakage, rain, etc. It’s difficult to avoid too much moisture.
C. The appropriate temperature
Molds often grow in warm and humid environments. It’s not easy to mold if the environment is too cold or too hot.