Parchment has been used for recording historical information since at least the 2nd century BC and makes an important contribution to our nation’s cultural heritage. Parchments are routinely assessed for degradation, but techniques with higher spatial resolution are needed to assess what is happening on the microscopic/nanoscopic scale. A group of scientists from Slovenia, Germany and the UK have been using I22, Diamond’s Small Angle Scattering and Diffraction beamline along with infrared spectroscopy at BESSY in Germany to study the degradation of a wide range of historic documents, to determine the effect of the environment and other factors such as the content of lipid on the degradation process.
“To preserve historic documents, managing material change that might lead to damage is vital,” explains Dr Matija Strlic, heritage scientist from Centre for Sustainable Heritage, University College London. These material changes can be induced by the environment or by components of the parchment document themselves. As an example, iron gall ink, the standard writing and drawing ink from the 12th to the 19th century, is particularly corrosive. The parchment itself, being made of animal skin, contains the protein collagen that can degrade to gelatine. Techniques currently used to study these processes, such as X-ray diffraction and thermal analysis can be destructive on both the macroscopic and microscopic scale, and benchtop IR spectroscopy does not provide sufficient spatial resolution.
|A historic score from 1750 AD written in iron gall ink. Due to use, lipids and soiling accumulated on the corner of the page, leading to extensive degradation as determined by Alenka Mozir, a PhD researcher from University of Ljubljana in Slovenia, using thermal analytical methods.|
Synchrotron-based Small Angle X-ray Scattering (SAXS) is capable of providing much higher resolution, enabling point-to-point mapping of structural features ranging from 1 – 100 nm. For cultural heritage artefacts where sample sizes should be as small as possible, this is a significant advantage. The group studied nine parchments with no historical or documentary value. Half of the parchments were artificially degraded, and the lipid content of the parchments extracted to varying degrees.
The results showed that higher lipid content (which could be the result of manual handling) led to increased degradation. The presence of iron gall ink also leads to changes in the way the parchment degrades, and that soiling also leads to pronounced degradation.
“We have suspected for some time that the level of lipid in parchment may be related to the acceleration of damage to the collagen. The combination of FTIR, X-ray diffraction and thermal analysis showed that we can detect these correlations. It is interesting that in the eye, lipids tend to initially protect the retina from damage but with ageing the presence of lipids seems to accelerate damage, we seem to have found a similar process in historic materials.”
Prof Tim Wess, University of Cardiff
A study of degradation of historic parchment using small-angle X-ray scattering, synchrotron-IR and multivariate data analysis Paper, Alenka Mozir, Lee Gonzalez, Irena Kralj Cigic, Tim Wess, Ira Rabin, Oliver Hahn, Matija Strlic; Analytical and Bioanalytical Chemistry (2011)
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