Autochrome

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Photographic Materials Conservation Catalog
Photographic Processes
Date: Initiated January 2012
Contributors: Luisa Casella, Tatiana Cole

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.

Autochrome


The Autochrome is a unique color transparency on a glass support.

"Georgia Engelhard in Sailor Coat", A. Stieglitz autochrome plate, Mark Jacobs Coll.
Autochrome plate in transmitted and reflected light
Unexposed autochrome plates

Historical Facts
Invented: Louis Lumiére, 1903.
Patented: Lumiére Brothers, 1904.
Main Period of Use: Between 1907-1935.
Historic Practitioners: Arnold Genthe, Alfred Stieglitz, Edward Steichen, Laura Gilpin
Contemporary Practitioners: Frederic Mocellin (http://www.autochromes.fr/)

Identification Characteristics
Image material: Translucent potato starch grains dyed red-orange, blue-violet, or green, between two layers of varnish, as well as metallic silver image particles.
Binder: Varnish layers and gelatin layer.
Support: Glass ranging in size from 4.5x10.5cm to 18x30cm

Autochrome structure

Analysis:
Non-Destructive - The potato starch grains are approximately 15 microns in diameter, and are visible under magnification with transmitted light. Positive identification of starch (as opposed to other color-screen materials) can be obtained by using transmitted polarized light, where the starch grains will appear to have a cross over them.
XRF would show presence of silver.
Destructive - FTIR would detect the protein (gelatine) and varnish layers, but GC-MS would be necessary to fully characterize them.

Micrograph of autochrome in transmitted and transmitted polarized light


Process Overview
The glass was coated with varnish, followed by a layer of dyed potato starch grains with a random distribution of color, followed by another layer of varnish. A fine black pigment would also have been applied directly after the starch grains in order to fill any vacancies present between them. A layer of silver-gelatin emulsion was then applied, followed by a final layer of varnish. During exposure of the plate in the camera, the starch grains act as filters of different wavelengths of light before it reaches the light sensitive silver-gelatine emulsion. The plate would then be developed and washed, and then chemically treated to bleach out the negative silver-based image. The plate would then be exposed a second time to light, thus creating a positive silver-based image, redeveloped and washed, and varnished a final time. When viewed with transmitted light, the dyed starch grains give the image a colored appearance in the mid and highlight areas. To protect the image, another plate of glass of equal size would have been affixed to the image.

Conservation and Treatment
Treatment procedures for autochrome plates are limited to stabilization of the glass components (support and cover glass) by placing them against one or between two additional glasses and binding them with tape (commonly Filmoplast P90); surface cleaning using air bulb; and stabilization of delaminating image layer (Waldthausen et. al. 2001).
The image surface is very sensitive to abrasion by contact so cleaning with a brush or cotton should be avoided.

Housing and Storage
Autochromes should be sealed to protect them from the damaging effects of oxygen and any air pollutants. They should be stored in a dry and cool environment to prevent degradation of both the silver image particles and dyes.
Freezing of autochrome plates is not advised due to risk of delamination of the image layer due to differential expansion and contraction of the various components.

Emergency Recovery
Exposure to water will cause great, irreversible damage to the autochrome image layer. This is commonly observed by the formation of green stains that are caused by the solubilization of the dyes present in the green filters.
Freezing is not advised due to the risk of image layer delamination as well as of risk of mechanical damage to the glass support due to pressure of moisture in microcracks.

REFERENCES

Conservation

  • Baldwin, G. 1991. Looking at Photographs: A guide to technical terms. Los Angeles: J. Paul Getty Museum/London: The British Museum Press. 10-11.
  • Casella, L. 2009. Autochrome Research at the Metropolitan Museum of Art: Testing methodology and preliminary results for anoxia light-fading. Topics in Photographic Preservation. Photographic Materials Group of the American Institute for Conservation of Historic and Artistic Works. 13:128-136.
  • Casella, L., M. Tsukada, N. Kennedy. 2011. Light-fastness of autochrome color screen filters under anoxic conditions. ICOM-CC 16th Triennial Meeting Preprints. Lisbon. Paper 1401. Paris: ICOM.
  • Casella, L., K. Sanderson. 2011. Display of Alfred Stieglitz and Edward Steichen autochrome plates: anoxic sealed package and lighting conditions. Topics in Photographic Preservation. 14:162-167. Washington D.C.: AIC.
  • Krause, P. 1985. Preservation of autochrome plates in the collection of the National Geographic Society. Journal of Imaging Science 29 (5):102-108.
  • Lavédrine, B. 2009. Photographs of the Past: Process and Preservation. Los Angeles: The Getty Conservation Institute. 76-81.
  • Lavédrine, B. 2013. The Lumière Autochrome: History, Technology, and Preservation. Los Angeles: Getty Conservation Institute.
  • Waldthausen, C., B. Lavédrine. 2002. An investigation into a consolidation treatment for flaking autochrome plates. In ICOM-CC 13th Triennial Meeting Preprints. Rio de Janeio. 2:664-660. Paris. ICOM.


Process and Historic Material


Contemporary Practice

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