Replication and study of the colouration of Edmond Becquerel's photochromatic images

Spectroscopies and Electron Microscopies Unravel the Origin of the First Colour Photographs

“…Edmond Becquerel's process of sensitizing silver layers has been replicated in the laboratory. The sensitization of real samples has been described in detailed in [16] and model samples have been introduced in [17] . Real samples are constituted by a sensitized 30 µm-thick silver deposit onto a 800 µm-thick brass support, whereas model samples consist in an integrally sensitized 1 µm-thick silver layer.…”

“…These first colour photographs motivated a long-lasting debate through the XIX th century between the supporters of a pigment hypothesis on the origin of these colours, the most famous being William de Wiveleslie Abney and Mathew Carey Lea and those who postulated an interferential origin to the colours of the photochromatic image, such as Wilhelm Zenker [13] and Otto Wiener [14] . Recent work allowed to reproduce Becquerel process in the laboratory [15,16] and to show that the sensitized layer, which is coloured during the exposition to light, is made of silver nanoparticles (NP) dispersed in a silver chloride grains matrix [15,17] . However, until now light has still not been shed on the nature of the photochromatic images colours.…”

“…We thus analysed several sensitized and coloured samples produced by our replication of Becquerel's process in the laboratory. [16] We will first present a study of the pigment hypothesis which involves chemical analysis of coloured layers produced by the Becquerel process, then we will discuss the interferential hypothesis in light of results on the morphology of these coloured layers. Finally, we will show that the silver nanoparticles dispersions contained in the coloured layers could be at the origin of the photochromatic images colours in the frame of a new plasmonic hypothesis.…”

Spectroscopies and Electron Microscopies Unravel the Origin of the First Colour Photographs

“…These first colour photographs motivated a long‐lasting debate through the XIX th century between the supporters of a pigment hypothesis on the origin of these colours, the most famous being William de Wiveleslie Abney and Mathew Carey Lea and those who postulated an interferential origin to the colours of the photochromatic image, such as Wilhelm Zenker and Otto Wiener . Recent work allowed to reproduce Becquerel process in the laboratory and to show that the sensitized layer, which is coloured during the exposure to light, is made of silver nanoparticles (NP) dispersed in a silver chloride grains matrix . However, until now light has still not been shed on the nature of the photochromatic images colours.…”

“…In this context, the XIX th hypotheses on the origin of the photochromatic images colours have to be revisited. We thus analysed several sensitized and coloured samples produced by our replication of Becquerel's process in the laboratory . We will first present a study of the pigment hypothesis which involves chemical analysis of coloured layers produced by the Becquerel process, then we will discuss the interferential hypothesis in light of results on the morphology of these coloured layers.…”