The Degradation of Daguerreotypes and the Relationship with Their Multi-Material Structure: A Multimodal Investigation.

Preserving and analytically examining daguerreotypes is particularly challenging because of their multi-material and multi-component structure. Various sensors have been exploited to examine mainly the image plates of the daguerreotypes even though the degradation goes beyond this component. Micro-analyses have been the preferred method due to the nanoscale structure of the image particles. In this work, we propose comprehensive multi-modal non-invasive sensing to investigate the corrosion products present in nine daguerreotypes from the Fondazione Alinari per la Fotografia (FAF, Florence, Italy). The methodology proposed includes chemical and morphological analyses: portable X-ray fluorescence spectrometry (pXRF), Raman microspectroscopy (µ-Raman), and micro-Fourier transform infrared spectroscopy in reflection mode (µ-rFTIR) for the chemical identification. For the first time, optical coherence tomography (OCT) was deployed to record the cross-sectional and morphological data of the relevant corrosion formations on daguerreotypes in a contactless way. The results allowed the characterization, in a non-invasive mode at a microscopic level, of a wide range of degradation products produced by the interaction of the different elements present in the structure of the daguerreotypes. The aim was to verify the performance of the proposed methodology and to link the chemical and physical complexity of the entire structure, disclosed by the state-of-art sensors, to the daguerreotype degradation. The results draw attention to the need to monitor not only the image condition but the whole object as a partially closed system in constant interaction internally and with the environment.

A Novel Transmittance Vis-NIR Hyper-Spectral Imaging Scanner for Analysis of Photographic Negatives: A Potential Tool for Photography Conservation.

This work illustrates a novel prototype of a transmittance hyperspectral imaging (HSI) scanner, operating in the 400-900 nm range, and designed on purpose for non-invasive analysis of photographic materials, such as negatives, films and slides. The instrument provides high-quality spectral data and high-definition spectral images on targets of small size (e.g., 35 mm film strips) and is the first example of HSI instrumentation specifically designed for applications in the photographic conservation field. The instrument was tested in laboratory and on a set of specimens selected from a damaged photographic archive. This experimentation, though preliminary, demonstrated the soundness of a technical approach based on HSI for large-scale spectroscopic characterization of photographic archival materials. The obtained results encourage the continuation of experimentation of HSI as an advanced tool for photography conservation.