Considerations about foxing stains in three paper collections ranging from the 16th to the 20th century
The article discusses the study of foxing stains in papers from the 16th to 20th centuries in Portuguese collections. The authors found that iron impurities, moisture absorbency, and new papermaking processes played a role in foxing stain formation. Visual observation and digital imaging were used to analyse selected batches of papers. Different paper types and historical periods showed varying degrees of foxing, with gelatine sizing and iron impurities being key factors. The presence of iron-containing impurities throughout the paper leaf was highlighted as a catalyst for the oxidation of cellulose,