Secrets of seventeenth century sealed letters revealed by dental X-ray scanners


Letterpacket DB-1627 was virtually unfolded and read for the first time since it was written 300 years ago. The letter contains a message from Jacques Sennacques dated July 31, 1697 to his cousin Pierre Le Pers, a French merchant, to obtain a certified copy of a death notice from one Daniel Le Pers. A watermark is also visible in the center of the paper containing the image of a bird. Credit: History Research Group Archive Unlock.

For the first time in the world, an international team of researchers has read an unopened letter from Renaissance Europe, without breaking its seal or damaging it in any way.

The research, published in Communications from nature, describes how an X-ray scanner used in dental research and ‘virtual display’ enabled the interdisciplinary team to read the contents of a securely and intricately folded letter that has remained unopened for 300 years, while retaining its valuable physical evidence.

A highly sensitive X-ray microtomography scanner, developed at Queen Mary University Dental Research Laboratories in London, was used to scan a batch of unopened letters from a 17th-century postal trunk filled with undelivered mail.

The senders of these letters had sealed them using ‘letter blocking’, the age-old process of intricately folding and securing a flat sheet of paper into their own envelope. Letter blocking was a common practice for secure communication before modern envelopes were used, and is considered the missing link between ancient physical communication security techniques and modern digital cryptography.

Until now, these letter packs could only be studied and read by cutting them, often damaging historical documents. Now the team has been able to examine the contents of the letters without irrevocably damaging the systems that secured them.







Computer generated unfolded animation of the sealed letter DB-1538. In our article we describe how “virtual display” was used to read the contents of sealed envelopes from 17th century Europe without physically opening them. Credit: History Research Group Archive Unlock.

Professor Graham Davis from Queen Mary University of London said: “We designed our X-ray scanner to have unprecedented sensitivity for mapping the mineral content of teeth, which is invaluable in dental research. But this high sensitivity has also made it possible to resolve certain types of ink on paper and parchment. It’s amazing to think that a scanner designed to look at teeth has taken us so far.

Dr David Mills from Queen Mary University of London said: “We have been able to use our scanners for X-ray history. The scanning technology is similar to medical CT scanners, but it uses much more intense X-rays that allow us to See the tiny traces of metal in the ink used to write these letters. The rest of the team were able to take our scanned images and turn them into letters that they could virtually open and read for the first time in more than 300 years. “

This process revealed the content of a letter dated July 31, 1697. It contains a request from Jacques Sennacques to his cousin Pierre Le Pers, a French merchant in The Hague, for a certified copy of a death notice of one Daniel Le Pers (full transcript and images available). The letter offers a fascinating insight into the lives and concerns of ordinary people in a tumultuous period in European history, when networks of correspondence kept families, communities and commerce together over great distances.

After X-ray microtomography scanning of the letter packs, the international team applied computational algorithms to the scanned images to identify and separate the different layers of the folded letter and ‘virtually unfold’ it.

Secrets of seventeenth century sealed letters revealed by dental X-ray scanners

A trunk of letters from the 17th century bequeathed to the Dutch postal museum in The Hague. The trunk belonged to one of the most active postal directors and postal directors of the moment, Simon and Marie de Brienne, a couple at the heart of the European communication networks. The chest contains an extraordinary archive: 2,600 “closed” letters sent from all over Europe to this communication hub, none of which was ever delivered. The sealed packets of letters in this trunk were scanned by X-ray microtomography and “virtually unfolded” to reveal their contents for the first time in centuries. Credit: History Research Group Archive Unlock.

The authors suggest that the virtual unfolding method and the categorization of folding techniques could help researchers understand this historical version of physical cryptography while preserving its cultural heritage.

“This algorithm takes us directly to the heart of a blocked letter,” explains the research team. “Sometimes the past resists scrutiny. We could have simply opened these letters, but instead we took the time to study them in search of their hidden, secret and inaccessible qualities. We have learned that letters can be much more revealing when they are. unopened. Using the virtual display to read an intimate story that has never seen the light of day, and has not even reached its intended audience, is truly extraordinary. ”


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More information:
Unlocking of history through automated virtual display of sealed documents photographed by X-ray microtomography, Communications from nature (2021). DOI: 10.1038 / s41467-021-21326-w

Provided by Queen Mary, University of London

Citation: Secrets of 17th Century Sealed Letters Revealed by Dental X-Ray Scanners (2021, March 2) Retrieved March 2, 2021 from https://phys.org/news/2021-03-secrets-17th-century- letters-revealed.html

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