kalotypii

Kalotypii, also known as calotype, is an early photographic process developed by William Henry Fox Talbot in the 1830s and announced in 1839. The term Kalotypii reflects a transliteration used in some languages, but in English the process is known as calotype. It produces a negative image on paper that can be used to make multiple positive prints, enabling reproduction of photographs for the first time.

The process begins with sensitizing paper by immersing it in a solution of silver nitrate and potassium iodide to form silver iodide on the surface. After drying, the paper is exposed in a camera, creating a latent image. Development is carried out with substances such as gallic acid or pyrogallic acid (with silver nitrate), which reduce exposed silver ions to metallic silver and reveal the image. The negative is then fixed with a caustic or fixer (commonly sodium thiosulfate) and washed. A calotype negative can be used to produce positives by contact printing onto salted paper or other supports, enabling multiple copies of a scene.

Calotypes offered the major advantage of reproducibility and a relatively wide tonal range, but they were slower to expose and the paper-based negatives were less sharp and more delicate than metal-based counterparts. The texture of the paper and the chemical processes also contributed to a softer image compared with later techniques. Despite these limitations, the calotype represented a foundational step in photographic history by introducing the concept of a reusable negative.

Its development influenced subsequent paper-based processes and helped shape the shift toward modern methods of image reproduction, culminating in later improvements such as albumen prints and wet collodion processes.