Reading ancient sealed documents

EPFL physicists reveal the last wishes of a Venetian woman from the year 1351 contained in a wax-sealed document, without breaking the seal. Using the fact that ancient inks in Europe are iron-based and X-rays cannot penetrate this heavy metal, X-ray tomography can scan through the entire volume of a book, without ever having to open it, to reveal the words written on the paper. The technology is being developed with the myriad of fragile documents at the State Archives of Venice in mind, in the context of the Venice Time Machine launched by EPFL and the Ca' Foscari University of Venice.

A Venetian lady is finally heard

The sealed document tells the last wishes of a Venetian woman named Catharuçia Savonario from the year 1351.

EPFL physicist Giorgio Margaritondo of the Laboratory for Quantum Magnestism explains, “We do not know why the document was never unsealed. Maybe the family disappeared, or there was an epidemic. There are many documents like that in the Venetian Archives. But we were able to read inside without a problem thanks to X-ray tomography, and let this young lady speak to us after so many centuries. It was an emotional experience.”

Margaritondo, who gave his honorary lecture at EPFL on December 14^th, elaborates, “What we found inside were details, facts, places in Venice that still exist, so it is very much a living document that can speak to us today. There is also a funny detail. She took the time to explain that she had chosen very expensive paper for her will, probably to show that she was a wealthy lady and not nobody.

“It is the first step towards the use of these techniques to read the documents at the State Archives of Venice.”

X-ray tomography and classification of inks

Many of the documents at the State Archives of Venice are too fragile to be opened and read. A non-invasive technique is required to see inside these documents without destroying them.

“Thanks to the use of iron-based inks that were used in Europe for more than 1000 years, we were able to read the text inside a closed document, a closed book, a closed will,” says EPFL physicist Fauzia Albertin. “X-ray tomography is the solution for preserving this heritage and shedding light on European history.”

Albertin had previously worked on an important step towards scanning the centuries of documents at the State Archives of Venice by classifying the different types of iron-based inks that were used in Europe over time.

Before revealing the contents of the sealed testament, the physicists developed their scanning technique with a scientific book from 17^th century that could readily be opened for comparison with the data obtained with X-ray tomography. The book was scanned, layer by layer, at EPFL’s PIXE laboratory for X-ray radioscopy and tomography platform. The scientists could therefore navigate through the X-ray data to read the text and drawings of the various pages.

Their technique differs from existing techniques that use a different frequency of light for the detection of modern plant-based ink. Also, in contrast to modern-day books, ancient documents present the challenge that the paper is very rarely flat, but rather warped or weathered by time. For the moment, the physicists are manually extracting the pages from the X-ray tomography scans. The next steps include building an algorithm that automatically detects the different pages.

The history of Europe

“Inside the Archivio di Stato there is the history of Europe,” says Margaritondo. “Venice was a very powerful entity, she controlled for example the international market of spices. By looking at the documents about the traffic in the port of Venice, we might be able to better understand the history of Europe.”