What are the brown spots that sometimes appear on works of art on paper?
‘Foxing’ is a general term that refers to the appearance of small, generally circular, brown spots and stains on works of art on paper. Foxing has many possible causes including mould and deterioration of metal impurities within the paper. Metal impurities would generally have been introduced during the paper manufacture process. Mould spores are everywhere in the environment and thrive on the cellulose that forms the paper as a food source, especially in high humidity.
