calotipia

Calotipia, also called calotype or talbotype, is an early photographic process developed by Henry Fox Talbot in the 1840s. It produced a permanent negative image on paper coated with silver iodide, from which multiple positive prints could be made, enabling reproducible photographs for the first time.

The process begins with coating paper with a solution that deposits silver iodide on the surface. After drying, the paper is exposed in a camera to form a latent image. The exposed sheet is then developed chemically, typically with gallic acid or pyrogallic acid, to render a visible negative. The image is fixed with a solution such as sodium thiosulfate to remove unexposed silver salts, making the negative stable. The resulting calotype negative is on paper and can be used to produce positives by contact printing, either on salted paper or other sensitized media, yielding multiple copies from a single negative.

Calotypes are noted for their soft, painterly tonal range and the ability to produce numerous prints from one negative. However, they are less sharp than later photographic methods due to the texture of the paper and the inherent softness of the negative. The process also required longer exposure times and careful handling of delicate sheets, limiting its practicality in some situations.

Significance and legacy: calotipia marked a major step in photographic history by introducing reproducibility and the negative-positive workflow that underpins modern photography. It influenced later processes such as the wet collodion and dry plate systems, and it remains an important milestone in the development of image-making technologies.