Science in Archaeology

This ‘science in archaeology’ project advances knowledge in the field of writing materials in later medieval Europe and especially slate which was used as a material of learning by scholars in Ireland (see Gaelic Learned Kindreds of Ireland webpage). The project is a collaboration between Prof Liz FitzPatrick, Archaeology, NUI Galway, Prof Hugh J. Byrne of the FOCAS Research Institute, Dublin Institute of Technology, and Dr Nessa O’Connor, National Museum of Ireland. The project was grant-aided by the Royal Irish Academy Committee for Archaeology.

Raman Spectroscopy



Raman spectroscopy in progress

Both FTIR and Raman microspectroscopies were employed to investigate surface deposits on late medieval slates from Smarmore, Co. Louth.  The collection of fifty-one slates are striking evidence of the writing materials of a learned cleric and a probable late medieval school, at Smarmore medieval parish church on the historic Louth-Meath border. The majority of the content of the Smarmore slates relate to plant-based medical recipes, most of which are vulneraries used in the healing of wounds, some are ecclesiastical in content and four are inscribed with polyphony. The work of Bliss (1965, 35-7) and the additions and revisions made to some of his findings by Britton and Fletcher (1990) confirms that the majority of the inscriptions are in late medieval Hiberno-English.

Smarmore, Inscribed, Slate, Inscription, FTIR, Later Medieval, Archaeology

Using FTIR on Smarmore NMI 1961.8a Later Medieval Inscribed Slate

Slates were used in different ways in the schools of later medieval Europe – some as a medium for permanent preservation of a record, others as a temporary means of keeping information that might later need to be committed to manuscript or to print (Willemsen 2008, 62-4). Slate is also known to have been used to make table-books which were small, portable books of thin leaves or plates of slate, held together with clasps. In many instances, inscriptions on slates are scratch marks on the surface, shallow and almost illegible, and usually over-written indicating multiple sessions of use.‌

It was first thought that dark yellow surface deposits on some of the Smarmore slates might be the remains of wax into which inscriptions were made leaving lightly incised impressions of lettering on the backs of the slates, but the results of Raman spectroscopy, applied in particular to Smarmore NMI 1961:8 and NMI 1961:12, suggests a different identity for those deposits. Results indicate that a complex pigmented substance was applied to the slate surfaces. What is best described as a yellow-brown ‘paint’, based on an organic dye substance, a charcoal-type carbon and quartz, all bound by an unidentified mordant (perhaps egg-white) was applied to the surfaces of slates.  By that means slates could have served as mediums for both permanent and semi-permanent records and, most importantly, they could have had repeated use simply by painting over the previous lightly incised inscriptions. All of the Smarmore inscriptions are lightly incised into the slate and many of the slate surfaces have palimpsests or erratically placed inscriptions, which suggests that slates had repeated use through the medium of a painted surface. The concept of painting slate surfaces, so that lightly incised inscriptions stood out when they were cut into a coloured surface, adds new knowledge to our understanding of late medieval writing materials.