Conservation conditions and humidity

The classic museum benchmark is 50% relative humidity and 20°C, within a few points; since 2014 the Bizot Group guidelines accept a stable band of 40 to 60% and 16 to 25°C for loans. Beyond that, wood swells, paint lifts, paper spots with mold. The loss is rarely an instant: an air handling unit fails over an August weekend, humidity climbs, and the damage is found ten days later. The insurance difficulty sits on the line between a sudden event, which is covered, and gradual deterioration, which fine art forms often exclude together with inherent vice and wear. What the insured can produce makes the difference: logger records of temperature, alarms, the maintenance log, condition reports before and after. Without continuous recording the adjuster can date neither the failure nor its effects. Basement storage and the containers of a freeport are particularly exposed.