From Wiki

Back to Photographic Materials Chapter List
Back to PMG Photographic Processes

This entry is a Draft

In progress: Seeking additional comments and images to develop this section

Photographic Materials Conservation Catalog
Photographic Processes
Date: Initiated January 2012
Contributors: Saori Lewis

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.


Historical Facts
Inventors: Alphonse Louis Poitevin, F. Joubert, C. M. Tessié du Motay, C. R. Maréchal, Joseph Albert
Patented: 1855 (British Patent No. 2815)
Important Development Dates:
1855 Collotype process was patented by Alphonse L. Poitevin in England. Poitevin used lithographic stone with albumen to create photo-sensitive plate.
1865 C. M. Tessié du Motay and C. R. Maréchal developed process using copper plate coated with gelatin.
1868 Joseph Albert developed process using glass plate coated with gelatin, which was the first commercially successful collotype process. Albert called this "Albertype."
1872 Albert-type Printing Company in Boston bought the rights to the process.
1873 Albert introduced the first cylinder press for collotype that was capable of printing large editions at high speed.
Alternate Names: Albertype or Albert-type, lichtdruck (German), photogype or phototypie (French), heliotype, artotype, phototint, photogelatin, hydrotype, ink photo, autogravure
Historic Practitioners: Commonly used for WWI postcards and posters in the 1930s and 1940s. Benrido ([1]) in Kyoto Japan is one of few commercial collotype printers in operation as of 2012.

Identification Characteristics
Image layer: Lithographic ink on paper
Color: black & white or full color
Support: Paper
Analysis: Fine reticulation pattern is visible at high magnification (>60x).

Basic Process Overview
A glass plate is prepared by coating with a layer of gelatin hardened with sodium silicate, then with gelatin mixed with potassium or ammonium bichromate. The second layer of gelatin is light sensitive once it is dried. When this plate is exposed to light in direct contact with image-bearing negative, the second layer of gelatin hardens relative to the amount of exposure to light through the gradation of the image. After exposure, the plate is soaked in water. During soaking process, the gelatin that did not harden swells laterally, creating warm-like reticulation pattern. Dampened plate is inked with oily lithographic ink, which is repelled by swollen high spots of gelatin, then pressed against paper.

Housing and Storage Considerations

  • Collotype prints should be stored in good quality paper-board folders, to protect from light, dust, and handling. Materials passing the Photographic Activity Test (P.A.T.) are suitable for use.
  • An ideal temperature and humidity are 68 degrees F (20 degrees C) +/- 2 degree drift and 50% +/-5% variation over 24 hours.

Emergency Recovery Tips

  • Handling wet paper can cause damage such as nicks, abrasions, and tearing.
  • Mold can develop on or within the papers.
  • Find step-by-step salvage technique for moldy paper in Preservation Leaflet 3.8: Emergency Salvage of Moldy Books and Paper[2]by Northeast Document Conservation Center (

Electronic Media Resources: WEBLINKS, AUDIO, DIGITAL

Printed Resources: BOOKS, ARTICLES

  • Baldwin, Gordon. 1991. Looking at photographs: a guide to technical terms. Malibu, Calif: J. Paul Getty Museum in association with British Museum Press.
  • Benson, Richard. 2008. The printed picture. New York: Museum of Modern Art.
  • Gascoigne, Bamber. 2004. How to identify prints: a complete guide to manual and mechanical processes from woodcut to inkjet. New York, N.Y.: Thames & Hudson.
  • Nadeau, Luis. 1997. Encyclopedia of Printing, Photographic and Photomechanical Processes.
  • Reilly, James M. 1986. Care and identification of 19th-century photographic prints. Rochester, NY: Eastman Kodak Co.

Back to Photographic Materials Chapter List
Back to PMG Photographic Processes