Calotype

The calotype, also known as the talbotype, was an early photographic process introduced in 1841 by the British pioneer William Henry Fox Talbot. It represented a landmark transition between the earliest experimental forms of photography and the more refined techniques that defined later nineteenth-century photographic practice. Based on chemically sensitised paper, the calotype enabled the creation of reproducible images, distinguishing it from competing processes. Its development formed a central part of the evolution of negative–positive photography and contributed significantly to the growth of both scientific and artistic photographic work.
The term calotype derives from the Ancient Greek words for “beautiful” and “impression”, reflecting Talbot’s aim to create images that combined aesthetic quality with reproducibility. Although ultimately surpassed by later methods, the calotype remains historically significant as a foundation for modern photographic reproduction.

Background and Early Experiments

William Henry Fox Talbot began experimenting with light-sensitive materials in the 1830s, motivated by a desire to fix images formed by the camera obscura. His earliest success came in 1835 with what he called the photogenic drawing process, in which paper coated with silver chloride visibly darkened under prolonged exposure. This method was a printing-out process, meaning the final image had to form fully inside the camera. Exposure times frequently exceeded an hour, making the process impractical for most subjects.
Several developments in the wider field of photography influenced Talbot’s work. Notably, the daguerreotype, publicly announced in 1839 by Louis Daguerre, introduced the principle of latent image development, whereby a faint or invisible image produced by brief exposure could be chemically developed into a visible photograph. Although Talbot was not the first to use latent images, he was the first to apply the concept to paper-based negative–positive photography, laying the groundwork for the processes that would dominate non-electronic photography into the twentieth century.

The Calotype Process

By late 1840 Talbot had adapted his photogenic drawing experiments into a developing-out process capable of producing images after exposure times of only a minute or two in bright sunlight. He patented this improvement in 1841, calling the resulting method the calotype or talbotype.
The key light-sensitive compound in calotype paper was silver iodide, created through a multi-stage chemical preparation:

• High-quality writing paper was first brushed with a silver nitrate solution and dried.
• The same sheet was dipped into potassium iodide, forming silver iodide within the paper fibres.
• This iodised paper, being largely insensitive to light, could be stored until required.

Before exposure, the iodised surface was coated with a gallo-nitrate of silver solution, a mixture of silver nitrate, acetic acid, and gallic acid. This sensitised the sheet, which was then lightly blotted and placed in the camera.
After exposure the paper was removed and developed by applying more gallo-nitrate of silver while gently warming it. Once the latent image appeared at full strength, the photograph was either:

• Stabilised using potassium bromide, leaving undeveloped silver halides only mildly sensitive to light; or
• Fixed using hot sodium thiosulphate (“hypo”), which dissolved remaining silver iodide and rendered the photograph completely insensitive to daylight.

The resulting calotype negative was translucent and could be used to produce multiple positive prints.

Printing and Image Characteristics

Although calotypes could be printed onto similarly prepared paper, Talbot’s earlier silver chloride-coated salted paper became the standard material for contact printing from calotype negatives. It was cheaper, easier to prepare, and aesthetically preferred by many photographers for its soft tonal qualities.
One recognised limitation of the calotype arose from the use of paper as the negative base. The fibres and surface texture of the sheet remained visible in the final print, producing a slightly grainy effect. Consequently, calotype images tended to be less sharp than daguerreotypes, which were recorded on polished metal plates and displayed exceptional clarity.
To counter these issues, photographers often waxed their negatives, increasing transparency and reducing the prominence of paper grain. This refinement significantly improved the tonal range and detail in calotype prints.

Comparison with the Daguerreotype

The daguerreotype process provided a single, direct positive image of great sharpness, making it particularly suited to portraiture. However, each daguerreotype was unique and could only be copied by re-photographing the plate.
The calotype’s greatest advantage lay in its negative–positive workflow, which permitted unlimited reproduction of prints from a single negative. This capability aligned strongly with scientific documentation, travel photography, and artistic experimentation.
Despite this, the calotype initially failed to surpass the daguerreotype commercially. Two principal factors contributed to this:

1. Talbot’s patent restrictions. In England, Talbot patented both his early processes and the calotype itself, requiring practitioners to obtain a licence. Daguerre, supported by the French government, had made his process publicly available without patent protection.
2. Image sharpness. The calotype’s paper base gave it a softer appearance, which some considered inferior to the daguerreotype’s crisp results.

Nevertheless, many photographers valued the calotype’s aesthetic qualities and its flexibility for creative manipulation.

Adoption and Regional Developments

In Scotland, where English patent law did not apply, the calotype flourished among early enthusiasts. The Edinburgh Calotype Club, one of the world’s first photographic societies, actively promoted the process during the 1840s. Scottish photographers David Octavius Hill and Robert Adamson produced influential calotype works, including the well-known 1845 portrait of a Native American visitor to Edinburgh, one of the earliest surviving photographs of an Indigenous North American.
In England the Calotype Society formed around 1847, though participation remained relatively limited due to patent constraints. After Talbot’s patent restrictions were lifted in 1853, calotype use expanded briefly but soon faced competition from newer methods.
British photographers also carried the calotype abroad. In India, for instance, surgeon John McCosh employed the process in 1848 to produce early photographic documentation, including an image of Duleep Singh.

Transition to Later Processes

By the late 1850s the collodion process—which used glass plates to create sharp, reproducible negatives—combined the strengths of both the calotype and the daguerreotype. It rapidly became the dominant photographic technique, effectively displacing the calotype.
Even so, during its period of prominence the calotype fostered a culture of photographic experimentation. Amateurs in Britain and across Europe adopted the technique for its expressive qualities and its perceived distinction from the commercially oriented daguerreotype trade.