Imaging Techniques

1) diffused light: we can illuminate the object with diffused light, i.e. irradiate it uniformly from every angle, a very important lighting mode to always guarantee, because even if it does not allow us to discover hidden details, it is essential to be able to make subsequent comparisons .

2) transmitted light: also called backlighting or transillumination, it consists in illuminating the object from behind, which will let the light leak out in a different way than the elements it contains.

3) grazing light: it allows to bring out many details such as pressure on the paper, hidden marks in writing, blind grooves, disappeared inks, erasing marks. It consists in pointing a light source on the object that affects it with a certain inclination.

1) X-rays: X-rays (λ 10 nm - 1 pm) are able to penetrate the matter considerably and can therefore allow reading even very thick layers that cover the writing, making them effective in cases of damage caused by fire that causes the phenomenon of agglutination or from water sticking pages to each other. The radiographic image is presented as a black and white photographic negative, in which the clear areas are those that have absorbed the radiation the most, since in fact each material has a different radiopacity, the ability of substances to be more or less crossed by X-rays. Among the techniques that exploit this radiation are fluorescence (XRF) and tomography.

2) UV: the use of ultraviolet rays (λ 400 nm - 10 nm) allows to differentiate and localize indistinguishable inks to the naked eye through the fluorescence technique, which exploits the characteristic of some substances to make themselves visible with different colors than their own chemical composition when they are hit by ultraviolet radiation, because they re-emit radiation of a longer wavelength. In this way it will be possible to restore legibility in texts that have been erased mechanically or chemically, or to differentiate ancient inks from modern ones, identifying fakes or later remakes.

3) IR: with infrared rays (λ 700 nm - 1mm) the techniques of thermography can be used, which is based on the emission of black body radiation by objects at room temperature in some bands of the medium-far infrared, and infrared reflectography, which considers the spectral band between 0.8 and 2.2 µm and exploits the ability of these rays to cross the layers and therefore enhance the legibility of writings covered by damage or mold. Another technique used with IR-ray acquisitions is false color infrared, or post-production image processing through the manipulation of RGB color channels.

4) Terahertz: a particular radiation found between infrared rays and microwaves (λ 10 cm - 1 mm) called Terahertz (100 µm - 1 mm) was used in the THESMA project for the study of Gadda's Quaderno di Campagna II and, in particular, for reading through sheets of attached paper and cartouches.

• X-ray tomography

  Fauzia Albertin's studies, presented at the International Seminar "Papers, pens, inks" (Bologna, 2019)

• False color infrared
• Applications of Terahertz on Gadda's Quaderno di Campagna II

1) RTI: The RTI (Reflectance Transformation Imaging) method, developed by the non-profit organization Cultural Heritage Imaging (CHI), allows an immersive study of the manuscript, through the acquisition of high-definition images and their recomposition and visualization through a navigation software in different ways. Born as a study tool in the field of cultural heritage, the RTI method, initially used for the study of artistic and archaeological artefacts, can be applied to the study of parchment and paper manuscripts, allowing the scholar an analytical definition of the object which, through the virtual reconstructed three-dimensionality, it allows to visualize the compositional stratigraphy. The acquisition involves a series of shots with a digital camera held in a fixed position, with positioning of the light at different heights and angles. The OA RTIbuilder software is used to recompose the images, while the display and navigation of the image are obtained through the OA RTIviewer software.

2) Photometric Stereo: this is a technique developed and presented around the 1980s by RJ Woodham (1980, 139-144), which is usually used in many areas of cultural heritage research, especially in archaeological studies and exhibition museum (Apollonio et al. 2021). The aim is to create accurate three-dimensional models of an object through the processing of multiple images acquired with different lighting conditions, which allow to conduct in-depth analyzes of the surface and of each component stratified over time, in order to be able to evaluate its state. conservation and reconstruct its genesis in great detail.

• RTI on Leopardi's Infinito
• Photometric Stereo

  The Vitruvian Man and Leonardo da Vinci's Codex Atlanticus analyzed with Photometric Stereo, studies by the team of Prof. Marco Gaiani (University of Bologna)

1) RAMAN: Raman spectrometry (or spectroscopy) is a molecular analysis methodology capable of providing a lot of information on organic and inorganic compounds.

• Raman Spectroscopy