Archivist Update: Glass Plate Negatives

There was no such thing as “point and shoot” during photography’s first century and a half. Until the mid-20th century, the photographer had to exert great physical effort, care, and time to obtain a single image.

Prior to the plastic-based negatives, photographic emulsions were made on glass supports, which we refer to as glass plate negatives.

Two types of glass plate negatives existed: the collodion wet plate, in use from the 1850s, and the silver gelatin dry plate, in use from the 1870s. Both processes are still in use by fine art photographers.

The Associated Press London Photo Library in the 1930s

Starting in the 1850s, collodion, a flammable liquid, was spread on a glass support, or plate, then placed into a bath of silver nitrate which turned the collodion into a photosensitive silver iodide. This process, including exposure and processing, had to happen immediately before the plate dried. 

While the wet collodion process had a five-minute exposure time before the plate dried, the dry plate negative allowed photographers to prepare their negatives in advance and develop images long after exposure.

Existing dry plate glass negatives are extremely fragile, requiring special storage conditions and handling by trained staff.

AP Photo Library

The Associated Press photo library, currently located in New York City, consists of over 5 million images, including prints, medium format, 35mm, and glass negatives. The library currently has around 4,000 dry plate glass negatives in its collection, most dating around 1929-1934. They are a mix of sizes from 2×3, 4×5, and 5×7.

About Associated Press Photos

Founded in 1846, the AP has covered all the major news events of the past 165 years, and has received 51 Pulitzers, including 31 photo Pulitzers.


The Associated Press New York Photo Library in 2014

Below is a gallery of scanned glass plate negatives from the Associated Press photo archive, including newly added images of Diego Rivera and Frida Kahlo.

Click on any image to launch the Archivist Update: Glass Plate Negatives gallery. 


Text by Megan Heflin, Manager of the Associated Press Photo Library in New York City. 

For questions about the Associated Press Photo Library, contact Megan:

To learn more about AP’s history or for questions about AP’s Corporate Archives, visit 


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Lead Image Caption: A damaged glass negative of Gov. Harry Moore of New Jersey with state trooper James A. McBride, near the home of Col. Charles A. Lindbergh. The trooper is pointing out the areas of interest in the kidnapping case, March 3, 1933, Hopewell, N.J. (AP Photo)


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