calotypes

Calotypes, also known as talbotypes, are an early photographic process developed by William Henry Fox Talbot and introduced in 1841. The process creates a paper negative coated with light-sensitive silver salts, which can be used to produce multiple positive prints by contact with light-sensitive paper. Calotypes represented one of the first practical methods for creating repeatable photographic images.

The basic workflow involves preparing paper coated with silver salts, typically by treating it with a solution that forms silver iodide on the surface. The paper is then exposed in a camera to light, producing a latent image. After exposure, the negative is developed chemically (commonly with gallic acid and other developing agents) and fixed to remove unexposed salts. The resulting negative can be used to make prints by placing it in contact with sensitized paper, usually salted paper, to produce positive images. The negatives were usually made on paper and tended to have a softer, more diffuse tonal range and a visible grain, which contributed to a characteristic aesthetic.

Historically, calotypes offered the advantage of true reproducibility: many positives could be produced from a single negative, unlike early daguerreotypes which yielded a single image. However, they required careful processing, could be less sharp due to paper texture and the development method, and were eventually surpassed by newer processes such as the wet collodion process in the 1850s. Talbot’s calotype laid important groundwork for modern photography by establishing the negative–positive printing concept and influencing the development of photographic chemistry and technique.