preservation index

n. A quantitative measure of the quality of a storage environment that is based on the impact of relative humidity and temperature on organic materials.


The concept of preservation index was developed by the Image Permanence Institute in 1995.


Nishimura 2011, 4 The preservation index, or PI, of a storage environment expresses the “preservation quality” of that environment, at the time of measurement, for organic materials (carbon-containing materials like plant and animal products, plastics, paper, dyes, etc.).