Paper-based documents have long been, and still are, the most important witness to human activity. Depending on the production technology and storage environment, paper can be a particularly long-lived organic material. However, most of the paper produced between 1850 and 1990 is not likely to survive more than a century or two due to the inherent acidity auto-catalysing its degradation. Cellulose is the most important structural element of paper and it is well-known that the rate of its degradation depends on its environment.
Traditionally, the condition of a paper-based object or of a whole collection is assessed visually, and simple physical and chemical tests are performed, such as the folding test or determination of the pH of paper using pH-indicator pens. While the folding test is performed in such a way that a paper corner is actually torn away, the pens leave some of the dye used as a pH indicator on the object. Neither of the two tests can be regarded as non- or micro-destructive. Nevertheless, surveys are necessary in order to reveal the condition of a collection, the general conservation needs and in order to plan preservation activities.
Historical paper can be an extremely diverse material: a number of production techniques and raw materials have been used throughout history and in addition, we have to take into account the diversity caused by natural degradation.
Our aims were the following:
- To develop a non-destructive method for characterisation of historical paper based on Near InfraRed (NIR) spectroscopy.
- To exclude the use of chemicals and sample preparation so that the technique could be used safely in a non-laboratory environment.
- To develop a portable instrument specially suited to the needs of practitioners, so that analyses of even the most valuable paper objects could be performed.
- To enable us to survey whole collections effectively by decreasing analysis time.
- To develop software enabling the user to perform statistical surveys of collections.
We have succeeded and are delighted to be able to present our achievements.
"Papermaking: The History and Technique of an Ancient Craft",
"Iron Gall Inks. On Manufacture, Characterisation, Degradation and Stabilisation",
"Ageing and Stabilisation of Paper",