LOGIN EXHIBITOR LOGIN VIP / Guest

Gelatin silver bromide print

The first monochrome emulsions using gelatin silver bromide were introduced in 1871 for the production of negatives on glass plates. The industrial manufacture of gelatin silver developing out papers was only finalized after the 1880s due to chemical improvements that allowed them to be made much more sensitive to light than aristotypes, the printing out emulsions of the previous era. Also more sensitive than the silver chlorides which, although developed, were used exclusively for contact prints, silver bromide allowed enlargement prints to be made without any blurring effect, therefore enabling the use of small-format negatives. This technological revolution, linked to the simplified process offered by the marketing of lightweight and easily transportable cameras for negatives, as well as the new availability of ready-to-use supports, would promote the development of an unprecedented market for amateurs and professionals alike.

So-called "baryta" papers, are made up of a layer of barium sulphate in between the support and the emulsion. Barium sulphate is a white pigment that increases shine and the whiteness of images when mixed with gelatine. In the case of matte baryta papers this layer is very thin, and agents such as starch are added (see enlarged image detail). The industrially manufactured paper media was sold in various textures (rough or smooth) and shades (pure white or ivory, for example). Over the course of the 1950s, optical brighteners – identifiable through their fluorescence under and ultraviolet lamp – were introduced to make the paper even whiter. From the end of the 1960s, manufacturers introduced plastic papers (known as RC for Resin Coated) in order to reduce the immersion time in processing baths and allow for faster drying. These were made up of a paper enveloped by two layers of polyethylene, one of them pigmented on the emulsion side and the other transparent on the support side. White pigment made from titanium dioxide may be the cause of red oxidisation spots. Some photographers, such as Jean Dieuzaide in France in the early 1980’s, spoke out against the use of these RC papers for both aesthetic and conservation reasons.

In order to produce the print, a latent image is developed in an alkaline chemical bath, which reduces the exposed silver salts into black metallic silver. After development, the image is neutralized into an acid stop bath, then fixed in a sodium thiosulphate solution which removes the undeveloped silver bromides that are still present in the emulsion. The print is finally washed in order to dissolve any traces of fixative, as its sulphur content can attack the silver grain over time. Although their natural tone is a neutral black, chemically developed prints can have several different tones and contrasts due to the use of toning baths. Sulphur toning, which appeared in the 1910s and is often called sepia toning due to the chocolate brown shades it produces, remained one of the most popular toning methods until the 1930s. Other, rarer toning methods, such as platinum or selenium, were also used.

Although gelatin silver bromide prints are quite light-stable, the effect of humidity and pollutants can create areas of metallisation or oxidisation of the silver in the image. Defective image processing, particularly the use of old fixative or insufficient washing time, alters the images, producing yellow or brown marks on the image or paper side.

Silver bromide printing was the most commonly used process in the 20th century, and although still marketed it is gradually becoming obsolete since the emergence of digital monochrome prints in the early 21st century.
Renger-Patzsch Albert, Still Life with Cherries, Collection Musée d’Art Moderne de la Ville de Paris
Renger-Patzsch Albert, Still Life with Cherries, Collection Musée d’Art Moderne de la Ville de Paris
Enlarged detail © ARCP / Mairie de Paris, Jean-Philippe Boiteux
Enlarged detail © ARCP / Mairie de Paris, Jean-Philippe Boiteux