manuscript lab

Dating, Forgery: Non-destructive Methods
Shrinkage temperature

Case Study: Dating of parchment

The structure and general deterioration pathways of collagen type I, the main constituent of processed skin, have been well studied and documented in the fields of medical research on skin, book preservation, and leather materials (Kennedy and Wess, 2003). In the absence of corrosive agents, its main natural ageing pathway can be described as the transformation of the collagen triple helix to a random coil, a process simplistically referred to as gelatinization (Fig.1).

Conversion of collagen (a) to gelatin (c)

It is customary to correlate the preservation state of parchment/leather with the shrinkage temperature, i.e., the temperature at which this transformation occurs in a water medium: the higher the shrinkage temperature, the better is the state of preservation, i.e., the greater the amount of intact collagen. In their seminal work on ancient skin-based materials, Reed and Burton have shown that shrinkage temperature scales well with age and can be used to date parchment and leather (Burton et al., 1959).

Correlation of shrinkage temperature with the age of parchment