Silver

#8C8C8CFormula AgEarliest recorded use 1839 (photographic)

9 eras9 artists20 colors

Photography is a silver medium. For a century and a half, every black-and-white photograph was an image made of metallic silver particles suspended in gelatin — the grey of a print is not a pigment at all but finely divided metal.

Origin

Silver halides — the chloride, bromide and iodide — darken on exposure to light, a property noted in the eighteenth century and turned into a process by Niépce, Daguerre and Talbot in the 1830s. The mechanism is that light frees electrons in the halide crystal, forming a latent image of a few atoms of metallic silver, which a developer then amplifies enormously by reducing the whole exposed crystal to metal. Fixing dissolves away the unexposed halide so the image stops changing. Gelatin, adopted from the 1870s, holds the crystals in suspension and made photography practical: dry plates that could be manufactured, stored and used months later replaced wet collodion that had to be coated, exposed and developed within minutes.

In art history

Silver appears across the photographic eras of this atlas, and the tonality of a print depends on how the silver is deposited. Daguerreotypes are silver amalgam on a mirror-polished plate, and their image is a metallic surface that shifts between positive and negative as the viewer moves. Salt prints and albumen prints give warm browns from very fine silver particles. Gelatin silver, the twentieth-century standard, gives the neutral to cool blacks associated with modern photography, and its tone can be shifted deliberately: gold chloride toning gives a cooler, more permanent image, selenium gives purple-browns and greater archival stability, sulphide toning gives the warm sepia of the nineteenth century — an effect that is now a filter and was originally a preservation treatment.

In the studio

Particle size determines everything. Large crystals are more sensitive to light and give a faster, grainier film; fine crystals give slow, smooth, high-resolution results. The visible grain of a fast black-and-white film is the silver itself. Silver images are physically robust but chemically vulnerable: incompletely fixed or washed prints retain residual chemistry that attacks the image over decades, producing the yellowing and silver mirroring seen on neglected prints, and atmospheric sulphur does the same. Properly processed, a gelatin silver print is one of the most stable photographic objects known, considerably more so than any colour process.

Afterlife

Digital capture ended silver's commercial dominance within about a decade, and the collapse of demand took Kodak's film business with it. Black-and-white silver materials are still manufactured, now for a committed minority, and the process has become a deliberate choice rather than a default — which is roughly what happened to egg tempera when oil paint arrived, five hundred years earlier.