Sheepskin may have been used in legal documents to aid fraud detection – study
Medieval and early modern lawyers in Britain used sheepskin for legal documents because it helped prevent fraud, new analysis has suggested.
Experts have identified the species of animals used for the documents dating from the 16th to 20th century.
Researchers at the universities of Exeter, York and Cambridge found that, of 477 documents dating from that period, most were written on sheepskins rather than goatskin or calfskin vellum.
They suggest this may have been because the structure of sheepskin made attempts to remove or modify text obvious.
Sheep deposit fat in between the various layers of their skin.
During parchment manufacture, the skin is submerged in lime, which draws out the fat, leaving voids between the layers.
Attempts to scrape off the ink would result in these layers detaching – known as delamination – leaving a visible blemish highlighting any attempts to change any writing.
According to the study published in Heritage Science, sheepskin has a very high fat content, accounting for as much as 30% to 50%, compared to three per cent to 10% in goatskin and just two to three per cent in cattle.
Therefore, the potential for scraping to detach these layers is considerably greater in sheepskin than those of other animals.
The continuing use of sheepskin over goat or calfskin in later centuries was likely influenced by their greater availability and lower cost, researchers say.
Sean Doherty, at the University of Exeter, the corresponding author, said: “We were surprised to discover that the deeds were made almost exclusively from sheepskin, as previous research has indicated that other non-legal documents were written on skins from a range of species.
“This potential preference for sheepskins could indicate that there was something particularly important about their use.”
He explained: “Lawyers were very concerned with authenticity and security, as we see through the use of seals.
“But it now appears as though this concern extended to the choice of animal skin they used too.”
Dr Doherty added: “The text written on these documents is often considered to be of limited historic value as the majority is taken up by formulaic rubric.
“However, modern research techniques mean we can now not only read the text, but the biological and chemical information recorded in the skin.
“As physical objects, they are an extraordinarily molecular archive through which centuries of craft, trade and animal husbandry can be explored.”
The study sets out that surviving texts hint at the use of sheepskin as an anti-fraud device.
The 12th-century text Dialogus de Scaccario – written by Richard FitzNeal, Lord Treasurer during the reigns of Henry II and Richard I – instructs the use of sheepskin for royal accounts as “they do not easily yield to erasure without the blemish being apparent”.
Professor Jonathan Finch, from the Department of Archaeology at the University of York, said: “What our research reveals is that there was a sophisticated understanding of the properties of different products and that these could be exploited. In the case of sheepskin parchment, its properties were used to prevent fraud by the surreptitious alteration of important legal documents.
“The structure of the skin clearly showed up any attempt to erase or alter the original text. The success of this study opens up new potential in the study of animal products over the historical period.”