As a sizing ingredient, alum has been one of the most important materials in the paper making process. Aluminum sulfate was used throughout the history of paper making. It has also been mentioned as a primary cause of paper degradation. Panduran is an eriochrome dye which reacts chemically to the aluminium ions present in alum, and in the process changes from yellow to blue to violet, thus detecting the alum content in the paper being tested. This reaction is not influenced by the pH value of the tested paper. Boards and papers with alum content are principally not suitable for long-term archival storage.
