Changes in temperature and relative humidity are among the major causes of deterioration that a finding can suffer. They can have harmful and irreversible effects, such as the separation of the painted layer from the painted plates or the oxidation in the case of metals. These thermo-hygrometric variations are even more harmful as they are higher and more sudden.
Conventional air conditioning systems inside museums usually allow to obtain an acceptable and adequate temperature for works of art. The main problem is the regulation of relative humidity values: a large influx of visitors or the seasonal trend can cause high variations and strongly affect buildings without insulation devices.
To contain these parameters, various interventions are possible.
First level of microclimatic control: border control
A showcase, and in general every museum container, allows the creation of a confined space (microclimate) separated from the external environment. The container therefore constitutes the first level of control of the internal microclimate, regardless of whether it is equipped with air conditioners or humidifiers.
A key element for the effectiveness of this first level is the good sealing of the enclosure, that is the ability to minimize air changes with the external environment. This can only be done with careful design of the cabinet that takes into account factors including: the opening system, the quality of the seals and the proper positioning of the gaskets, the use of inert materials and with low levels of hygroscopicity.
Second level of microclimatic control: passive control
A good seal of the showcase is possible to combine a further control of the hygrometric stability: the insertion of specific buffer materials, which allow to reduce the fluctuations of the relative humidity.These are sheets or blocks composed of a particular silica gel which has the characteristic of being calibrated according to precise relative humidity values. This buffer material is able to release or capture moisture in order to keep the level stable in the atmosphere
Third level of microclimatic control: active control
The highest level of control involves providing the window with a real mechanical air conditioning system. The cases in which the active control is required are determined by precarious conditions of the product and by environments with critical thermo-hygrometric properties.The display cabinet is designed and designed according to the system required, in fact the relative delivery and return pipes must be provided, a suitable air circuit to prevent overheating and a simple access to allow the operators to carry out periodic checks.