Salted Paper and Calotype Prints

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Photographic Materials Conservation Catalog
Photographic Processes
Date: Initiated June 2012
Contributor: Amanda Maloney, Stephanie Watkins

The Photographic Materials Conservation Catalog is created and maintained by the Photographic Materials Group of the American Institute for Conservation for the convenience of the membership. The treatments, methods, or techniques described herein are provided for informational purposes. The reader assumes responsibility for any application results or interpretation of information.

Salted Paper and Calotype Prints[edit | edit source]

Historical Facts
Invented: The first viable paper negative process was developed by William Henry Fox Talbot in the late 1830s. In 1847 Louis-Désiré Blanquart-Evrard developed a simplified version of Talbot’s formula and published it in France.
Patented: The first salt-print negative process was patented by William Henry Fox Talbot in England 1841 and called a calotype.
Historic Practioners: Talbot, Hill and Adamson, Louis-Désiré Blanquart-Evrard, Gustave Le Gray, Édouard Baldus, Heri Le Secq,
Contemporary Practioners:

Identification Characteristics
Image layer: The image is formed by silver deposited directly in the paper support.
Color: Range from warm brown to cool gray tones.
Support: paper, initially stationery, later wove papers that can withstand prolonged water immersion
(Non-destructive) XRF can be used to identify the silver image and also detect sulfur if the image has been fixed in sodium thiosulfate. (Destructive) GC-MS may be used to identify coating materials.

Basic Process Overview

Types of Deterioration

Housing and Storage Considerations
Temperature: A stable temperature between 18 and 30°C is necessary to avoid embrittlement, melting, or developing a bloom. Cold storage is not advisable unless rigorous handling and acclimatization procedures are in place.
Relative Humidity: Between 30% and 50% to avoid saponification and biodeterioration.
Housing: There are a variety of good choices of paper and plastic materials that have passed the PAT and are suitable for housing paper. One must consider all factors (research, access, preservation, exhibition, art in transit) and balance the pros and cons for a specific collection.

Emergency Recovery

Helpful Treatment Techniques, Things to Know, and CAUTIONS!


Process and Historic Material Root, M.A. 1864. The Camera and the Pencil, History of the Heliographic Art, Philadelphia Scully, France and Osterman, 2009, Mark, "Scully and Osterman" website:
Contemporary Practice

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