The sources of stains on paper can vary widely. Today, I will focus on foxing specifically. Does your document or work of art on paper have small, ovular stains or spots? These discolorations are commonly referred to as foxing. The source of these blemishes has been researched since the 1930s.
Potential causes are often theorized to be impurities residing within the paper and present during paper production. These impurities include a variety of metal ions, such as copper and iron. The oxidizing of these metal inclusions is what causes the discoloration. Another potential source of discoloration is bacteria or fungi. These could be introduced during the creation of the paper sheet, or during the creation of the work of art. For instance, many printmaking methods involve dampening the sheets of paper prior to printing on it. Engravings, etchings, lithographs, mezzotint and aquatint are some examples. The practices of the artist and cleanliness of their work environment, tools and materials can impact the possibility of the introduction of mold spores or bacteria. For example, if the dampened paper was left overnight, or in a contaminated vessel, bacteria or fungi that can cause foxing may be introduced to the work of art on paper or paper-based document. There may be other potential causes of foxing, yet to be discovered by conservation scientists. In the meantime, there are a variety of methods a trained conservator can use to reduce and eliminate these undesirable paper stains. If you have a paper-based artwork or manuscript that requires stain reduction, visit the contact page to arrange an evaluation.