Virtual X-ray Reading (VXR) of Ancient Administrative Handwritten Documents

The study of ancient documents is too often confined to specimens of high artistic value or to official writings. Yet, a wealth of information is often stored in administrative records such as ship records, notary papers, work contract, tax declaration, commercial transactions or demographic accounts. One of the best examples is the Venice Time Machine project that targets a massive digitization and information extraction program of Venetian archives. The Archivio di Stato in Venice holds about 80 kms of archival documents spanning over ten centuries and documenting every aspect of Venetian Mediterranean Empire. If unlocked and transformed in a digital information system, this information could change significantly our understanding of European history. We are exploring new ways to facilitate and speed up this broad task, exploiting x-ray techniques, notably those based on synchrotron light. . Specifically, we plan to use x-ray tomography to computer-extract page-by-page information from sets of projection images. The raw data can be obtained without opening or manipulating the bounded administrative registers, reducing the risk of damage and accelerating the process. We present here positive tests of this approach. First, we systematically analyzed the ink composition of a sample of Italian handwritings spanning over several centuries. Then, we performed x-ray imaging with different contrast mechanisms (absorption, scattering and refraction) using the differential phase contrast (DPC) mode of the TOMCAT beamline of the Swiss Light Source (SLS). Finally, we selected cases of high contrast to perform tomographic reconstruction and demonstrate page-by-page handwriting recognition. The experiments concerned both black inks from different centuries and red ink from the 15th century. For the majority of the specimens, we found in the ink areas heavy or medium-heavy elements such as Fe, Ca, Hg, Cu and Zn. This eliminates a major question about our approach, since the documentation on the nature of inks for ancient administrative records is quite scarce. As a byproduct, the approach can produce valuable information on the ink-substrate interaction with the objective to understand and prevent corrosion and deterioration.