There are a few reasons why images fade on thermal paper. The usage of a dye and a type of co-reactant technology is sensitive to ultraviolet lighting. The rate of fading and the degree in which it fades can depend on the kind of light it's being exposed to, for instance, office lighting would take longer to cause thermal paper to fade whereas direct ultraviolet rays can cause fading rather quickly. Also, it depends on how the image on the paper was produced, if it isn't stable, this can also cause a fast degree of fading. The intensity of ultraviolet rays can also determine the rate of thermal paper fade.
This results in proper storage of unused thermal paper. The product should be stored in an area with acceptable environmental conditions with no lighting, a relative humidity percentage range of 45% to 65%, and a temperature of below 77 degrees Fahrenheit. If these environmental parameters are acceptable, then the longevity of a stock of thermal paper should last from 5 to 7 years.
Sometimes exposure to certain chemicals or solutions can cause issues with thermal paper degradation. Thermal paper should be kept away from the following: organic solvents, ammonia, petroleum solvents, thermal systems that are contrary to the thermal paper itself, plasticizers, cleaning solutions, diazo copy paper of the wet variety, carbon and carbon less papers, coast coated papers, papers with tributal phosphate, certain types of oils, and prolonged exposure to water.