How to measure temperature and relative humidity. Instruments and instrumental problems

Temperature and humidity are responsible, in a direct or indirect way, of a number of deterioration mechanisms, as documented in some chapters of this book. In conserving tangible cultural heritage, the most outstanding effect is the visual appearance of damage or other deterioration products, that may be more or less easily restored, but the key problem is to recognize the causes that have generated the damage and undertake mitigation actions to stop or reduce the deterioration rate. Any object interacts with the surrounding environment, e.g. exchanging heat, moisture, gaseous species and particulate where the micro-environmental conditions can be favourable to the acceleration of chemical reactions or microbiological activity. In any case, microclimate plays a fundamental role and the key physical variables should be measured to know their relevance in the ongoing decay and to control them at levels more convenient for preventive conservation. In other terms, we should have a clear idea of what may be happening and investigate environmental forcing and object response to verify if they fill within the range of sustainability and acceptable preservation.