Spectroscopy is a technique that gives us an insight into which materials were used to create certain pigments in different eras. By using this technique on manuscripts, scholars can find out information about their provenance which they may not be able to discover any other way.
Raman spectroscopy, developed by the scientist Sir V.C. Raman in 1928, is a useful technique for manuscript study. It is not a destructive process, making it ideal for analysing the materials used in the paint and ink of old and valuable artefacts. This information can be useful for identifying a forgery as the specific materials used at the time are unlikely to have been reproduced exactly in the process of forgery. The method can also be informative on trade routes of the time. Lapis lazuli, for example, was highly valued for making expensive blue pigment, and can be found in the region of Afghanistan, which shows that there were trade routes from Afghanistan to Britain in the medieval era.
Medieval manuscripts often contain iron gall ink, which was prepared by adding iron to tannic acid extracted from oak galls made by insects, such as the gall wasp, laying their eggs in the tree. Iron gall ink is difficult to erase and darkens with age as the iron oxidises.
Any gold leaf, as can be seen in this example of a book of psalms from Worcester (c. 1200), was applied before the colour. In early manuscripts glue was used and in later ones gesso was rubbed on the page and then the gold leaf burnished until sufficiently lustrous. It is also a more prevalent feature of twelfth-century manuscripts.
The colour yellow was often produced using yellow ochre, and red using red ochre or haematite, an iron ore. These have been mined in the Forest of Dean nearby in Gloucestershire since the thirteenth century. Malachite and Verdigris were both used for green paint and blue was frequently made out of azurite, basic copper (II) sulphate. The luxury of lapis lazuli was normally saved for painting the robes of the Virgin Mary as it was expensive.
Although none of the books in the Worcester Cathedral Library have been analysed using spectroscopy, we have some idea of the material that might have been used to make them. In this tenth-century copy of Bede’s work about grammar and poetry, the ink used would probably have been iron gall ink. The red ink may be made of red ochre and the blue ink made of azurite.
This pre-twelfth-century manuscript has lines scored with an awl or the back of a knife.
The lines of this fifteenth-century missal (prayer and liturgical book) would have been scored with silver, graphite or lead. It has two columns, a characteristic of most manuscripts after approximately 1170.