Photographic Processes: 1839 – 1889


COLLODION NEGATIVE (wet-plate collodion), 1851-1885

Silver-based negative on glass with collodion (nitrated cellulose dissolves in ether and alcohol) as a binder to hold light sensitive materials

A solution of collodion and potassium iodide is poured over a glass plate leaving a clear film containing halide. The plate is then dipped in a solution of silver nitrate to form light sensitive silver halide on and just under the collodion surface. After being exposed in the camera while still wet (hence wet-plate), the plate is developed using pyrogallic acid (later ferrous sulfate), washed and fixed in sodium thiosulfate (later potassium cyanide). Once dry, the plate is coated with a protective varnish to prevent the silver image from tarnishing.

Hand-pouring of chemicals results in an uneven edge of the image on the glass. The corner of the negative where the photographer's thumb held the glass during coating remains chemical-free.

Mathew Brady. Ambrotype, late 1850s. [zoom]
Quarter plate
Additional images:

The ambrotype process produces a collodion glass negative which, when viewed against a dark background, creates the appearance of a positive image. When viewed against a light background, however, the image is revealed as a negative.

Unidentified. Page from the Gardner Family Album, ca. 1871. [zoom]
Tintype (left), albumen prints (center & right)

Capturing an image with the 8 x 10 in. sliding-box camera (right) required the photographer to perform an uninterrupted series of tasks. He prepared the wet plate collodion plate in the darkroom, loaded the camera, and posed the subject. He then focused the image, exposed the plate by lifting the lens cover by hand for the required time, removed the plate, and brought it back to the darkroom for immediate processing.

On loan from the Stephan and Beth Loewentheil Family Photographic Collection.

Samuel J. Mason. “Views of the Entire Falls with Yourself and Friends in the Foreground, 1870s. [zoom]
Albumen print, 5 5/8 x 8 1/8 in.

This photograph bears the hallmarks of an image printed from a wet plate collodion negative. The top corners of the negative remained chemical free where the photographer’s thumb held the glass during coating, resulting in a black corner on the positive print. The water shows no detail because of the slow shutter speed. Clouds do not appear because the wet-collodion process was sensitive only to blue light. While warm colors appear dark, cool colors such as the blue sky and white clouds are uniformly light.

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