Medieval Lawyers Used Sheepskin Parchment to Prevent Fraud and Forgery
Archaeologists tracing the evolution of British legal practices discovered one area where innovation was discouraged: the parchments for documents. From the 13 th to the 20 th century AD, British lawyers were scrupulously consistent in their use of sheepskin parchment for legal documents, choosing to write on this type of paper almost exclusively.
A team of researchers from the Universities of York, Exeter, and Cambridge recently completed an exhaustive study of the parchment-using habits of British solicitors and barristers, going all the way back to the medieval era.
Before beginning the study, they expected to find examples of lawyers using other types of commonly manufactured parchment, including goatskin and calfskin, as an alternative to sheepskin. But it seems old-time legal practitioners were slavish in their devotion to sheepskin, and quite sheepish about switching to anything else.
A medieval sheepskin legal document parchment (a) versus a paper legal document (b). (Heritage Science)
The British Legal Profession’s Sheepskin Parchment Heritage
As reported on March 25 in the journal Heritage Science, the researchers analyzed proteins extracted from 645 British legal documents dating from the 16 th to the 20 th century. More than 96 percent of these samples were discovered to be made from sheepskin.
This confirmed the results of past studies on hair fibers and follicle patterns that showed a heavy preference for sheepskin in documents preserved from the 13 th to the 19 th century (those studies were considered somewhat less definitive than this latest research).
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In the remaining samples, the proteins collected were slightly degraded, which made it impossible to determine if the parchment skins had come from sheep or goats, raising the possibility that the use of sheepskin was actually universal during this time period.
At first consideration, this overwhelming reliance on one type of parchment may seem odd. But there’s a very good reason why British lawyers were loyal to sheepskin parchment, according to the archaeologists who carried out this new study.
It turns out sheepskin has certain properties that make it highly resistant to alteration, which makes sheepskin parchment the ideal choice for preventing fraud and forgery. “Lawyers were very concerned with authenticity and security, as we see through the use of seals,” said Sean Doherty, a University of Exeter archaeologist who led the joint study. “But it now appears as though this concern extended to the choice of animal skin they used too.”
But why, it must be asked, was sheepskin parchment so difficult to alter? What was the source of its anti-fraud properties?
The key fact here is that sheepskin in its natural state has a much higher fat content than other types of animal skin. Levels in the 30 to 50 percent range are normal, while goat and cattle skin only have fat content percentages in the single digits.
Sheep are prodigious fat absorbers and much of it is stored in their skin. When this skin is processed in lime to make parchment, the fat is stripped away, leaving behind deep voids between the skin layers.
Once the final product is dried and converted to parchment, what remains is a flat, pliable surface that is not easy to modify once it has been written on. Any attempts to scratch off existing ink will leave behind visible marks that function as telltale signs of forgery and trickery.
The high-fat content of sheepskin parchment was perfect for preventing forgery and fraud in legal documents (goat and calf skins were not near as good). (Heritage Science)
Harvesting History from Tragically Neglected Sources
In the past, legal documents were considered poor resources for historical research. Most were deeds of various types filled with endless sections of repetitive legalese.
Tons of legal documents have been discarded, burned, or repurposed since the medieval era, and this practice became especially common after the Land Registry Act of 1925 eliminated any need to keep such documents in perpetuity. Nevertheless, because they were produced in such volume many samples from different time periods remain extant in various collections.
Fortunately, scientific and technological developments have progressed to the point where these old, dry documents can now be analyzed in a variety of ways, any of which could reveal previously unsuspected nuggets of valuable information.
“Modern research techniques mean we can now not only read the text, but the biological and chemical information recorded in the skin,” Doherty explained. “As physical objects they are an extraordinarily molecular archive through which centuries of craft, trade and animal husbandry can be explored.”
The archaeologists who employed these research techniques in this most recent study were initially interested in finding out precisely what type of materials lawyers had used to create written records down through the centuries. Once they identified a unitary pattern, they wanted to know the reason for the law profession’s choice of sheepskin as their go-to medium.
While the conclusion they reached is logical, given the evidence they collected, their theory isn’t based entirely on speculation.
In a surviving 12 th century text, Richard FitzNeal, Lord Treasurer to Henry II and Richard I, prescribes the use of sheepskin for all royal accounts, stating that “they do not easily yield to erasure without the blemish being apparent.” Commenting in the 17 th century, Lord Chief Justice of the King’s Bench Sir Edward Coke strongly recommended the use of parchment instead of paper, because “the writing upon these is least liable to alterations or corruption.”
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The researchers note that sheepskin was available in great quantities and at a relatively low cost in later centuries, which may have helped keep it in use even after paper-making technology had improved.
A north-central European type of finished parchment (made of goatskin) stretched on a wooden frame. (Michal Maňas / CC BY 2.5)
Dusty Documents and Hidden Biomolecular Codes
Needless to say, the success of this research project could set an example that other archaeologists and historians will be motivated to follow.
“We know so little about these documents, despite the fact that there are millions worldwide,” Doherty observed.
These “biomolecular archives,” which have been kept stored away gathering dust for centuries, could be a goldmine of valuable information, if the proper techniques are applied to fully decode their secrets.
Top image: Image of a sheepskin parchment analyzed as part of the recent study proving that sheepskins were perfect for preventing forgery and fraud on legal documents. Source: Dave Lee / University of Exeter
By Nathan Falde