JAIC 1999, Volume 38, Number 2, Article 2 (pp. 124 to 143)
JAIC online
Journal of the American Institute for Conservation
JAIC 1999, Volume 38, Number 2, Article 2 (pp. 124 to 143)

DIFFERENCES IN IMAGE TONALITY PRODUCED BY DIFFERENT TONING PROTOCOLS FOR MATTE COLLODION PHOTOGRAPHS

SYLVIE PENICHON



4 STRUCTURE OF PRINTING-OUT PAPERS

In printing-out papers, the sensitive material is silver chloride associated with an excess of soluble silver salts capable of absorbing halogen liberated by the action of light. The fast darkening of POPs is a consequence of this excess of soluble silver salts contained in the support itself, in the binder, or in the emulsion. The image becomes visible upon exposure to light, without the action of a developer. It consists of metallic silver in a very fine state of division (photolytic silver). The tone of the image depends on the size, distribution, and morphology of the silver particles (smaller particles absorb the smallest wavelengths and display a warm, reddish tone; bigger particles tend to give prints of cooler tone). Unlike albumen papers, where the silver particles are small and concentrated near the surface of the binder, emulsion papers have large silver particles that are spread uniformly in the binder (Lavédrine 1990).


Copyright © 1999 American Institute for Conservation of Historic and Artistic Works