a stain typically on paper, caused by prolonged exposure with an acidic mat board. Mat burn tends to have a darkening effect around where the window was creating a kind of framing effect.
Synonyms in English
Mat burn creates a darkening edging around where the window of the mat was, but can also darken any area in contact with an acidic mat. Poor quality mats are created from paper with heavy wood pulp content, which is chemically unstable and acidic. As the mat ages, the wood pulp decomposes, releasing acid which migrates to absorbent paper below. Displaying and storing works in archival quality mats containing no wood pulp can mitigate this kind of damage.
Ellis, Margaret H. 1995. The Care of Prints. Altamira Press. ISBN 9780761991366
Mat Burn. AICCM. Visual Glossary. http://www.aiccm.org.au/visual-glossary (accessed 16 March, 2014).