Collodion Glass Plate Negative

About

The collodion glass negative is a monochrome negative photograph on glass.

Paris. Le Panthéon, Gustave Le Gray, 1859, 51 x 42 cm, bibliothèque Historique de la Ville de Paris (négatif changement de polarité)

Historical period of production and use

Described in 1850 by the French Gustave Le Gray and in 1851 by the Englishman Frederick Scott Archer, it was widely used until the 1880’s and was the dominant negative process until this date. It is not the first negative process using glass as medium. In fact, in 1847 Claude Félix Abel Niépce de Saint-Victor (Joseph Nicéphore Niépce’s nephew) developed the first feasible glass process in the form of albumen glass plate negatives. Niépce de Saint-Victor uses the glass because this material, mineral and transparent, enables to insulate the photographic image from its substrate, increasing significantly the sharpness of the positive image. The albumen process, even if producing images of excellent sharpness, requires however very long exposure times, which is why it was quickly overshadowed by the more sensitive collodion process.

Manufacturing

The glass plate used is cut to the required size beforehand and thoroughly cleaned. The collodion, obtained by dissolving cellulose nitrate in alcohol and ether to which halides – iodides and bromides – are added, is manually evenly poured onto the centre of the glass plate. Before complete drying, the collodion coated plate is sensitized by immersion in a silver nitrate solution and then exposed immediately in a photographic camera while still wet. The latent image obtained is then immediately developed in an ammonium iron sulphate or pyrogallol solution. The image is then fixed in a potassium cyanide or sodium thiosulphate solution and washed. Finally, the dried plate is generally varnished to protect the collodion layer against abrasion and to prevent silver tarnishing. In order to improve the quality of prints, photographers frequently work on the negatives: portraits are retouched using a graphite pencil and skies in landscapes are covered with inactinic paper or gouache painting. Collodion glass plate negatives are then printed by contact, in the majority of cases on albumen paper.

This process has the advantage of taking far less time than the albumen glass plate process, allowing shooting of less than three seconds. On the other end it has the significant drawback of having to be used wet, because when it dries, collodion becomes waterproof to laboratory chemicals (developer and fixer). The photographer is than forced to expose and develop his negative right after its preparation, obliging him to take their developing laboratory with them while taking pictures outdoors. This process was therefore rapidly adapted in order to overcome this difficulty. In 1853, Marc-Antoine Gaudin introduced the use of hygroscopic substances (sugar, honey or glycerine), which allow a certain level of porosity in the collodion, allowing the plates to be prepared in advance, used at a later date and developed subsequently. Taupenot proposes its "dry collodion processes" in 1855. The following year, Dr. Hill Norris launched the first ready-to-use plates in England. However, dry collodion processes remained rare and mainly used for landscape photography, as their sensitivity is clearly inferior to that of wet plate collodion processes.

Identification

Collodion glass negatives come in non-standard sizes; the thickness of the glass is irregular, often greater than that of industrial glass (so-called “printing glass”), and the edges are often poorly cut. The image layer is uneven at the edges and may show drips or fingerprints. The negative image has an overall milky tone. There is often an additional layer of varnish that gives it a slightly yellowish tint.

Deterioration

Collodion glass negatives may exhibit mechanical damage typical of the glass substrate: scratches, cracks, breaks, gaps, and manufacturing defects. The collodion layer may lift at the edges, crack, or shrink; in the latter case, it creates a more or less regular network of cracks. The silver image may develop a fairly strong silver mirror effect if the image layer is not varnished.

Credits

Visual Glossary of Photographic Processes © ARCP / Mairie de Paris, 2023

Glossary

Albumen Print

Aristotype

Autochrome

Carbon Print

Chromogenic Prints

Collodion Glass Plate Negative

Portrait Crayon

Cyanotype