Foxing of Watercolor Paper and Environmental Control as Preventive Actions

In Singapore's hot and humid climate, watercolor papers are particularly prone to a paper oxidation issue known as foxing, which refers to the discoloration forming yellowish-brown stains on paper, changing the visual outcome of the watercolor artworks. This research investigates two most popular types of watercolor paper, made from 100% cotton and cotton-wood-pulp mixture. Foxing was generally categorized into two types: biotic and abiotic foxing caused by fungi activities and the presence of metallic contaminants catalytic fungi growth. However, recent hypotheses further relate it to heterogeneous cellulose structures. Watercolor paper is typically produced in a well-controlled environment, which should theoretically reduce the occurrence of foxing, catalyzed by metallic contaminants. The research involved a comprehensive analysis of aged samples, from old watercolors, dating back to the 1990s and fresh watercolor paper samples. focusing on understanding the origin and causes of watercolor paper foxing based on cellulose content & structures. By comparing 100% cotton and cotton wood-pulp blended watercolor paper, the susceptivity of foxing was hinted to be related to cellulose packing density. These findings will support further research in developing strategies for the conservation and storage of watercolor artworks.