Mold on Paintings: Causes, Damage, and Conservation Treatment. Early presence of mold is often signaled by a musty odor, faint speckling, or a hazy bloom on surfaces—especially after a humidity spike or HVAC interruption. If you suspect mold, don’t attempt to wipe or “clean” it. Isolate the work, stabilize the environment’s humidity and temperature levels, and contact a conservator promptly to prevent the problem from becoming structural rather than merely superficial.