Collotype is a printmaking process invented in the mid-19th century, which produces a photographic image on a flat surface. The word "collotype" is pronounced as [ˈkɒlətaɪp] with stress on the second syllable. It is spelled with the prefix "collo" derived from the Greek word for glue or gelatine, and "type" indicating a form or image. The combination of these two words gives rise to "collotype," which refers to a printing technique that uses a gelatine coating on a flat surface to transfer photographic images.
Collotype, also known as phototypography, is a type of photomechanical printing process that produces high-quality and detailed reproductions of photographs or other fine art images, typically with ink on paper. It was first developed in the mid-19th century by Alphonse Louis Poitevin, a French chemist, and remains influential in the realm of fine art printing.
The collotype process begins with a glass or metal plate, meticulously coated with a light-sensitive gelatin solution and then exposed to a photographic negative. The plate is exposed to ultraviolet light through the negative, causing the gelatin to harden in proportion to the varying density of the original image. This results in a plate with microscopic variations in hardness, which is a direct representation of the greyscale tonal values of the original photograph.
To print an image using collotype, the prepared plate is first inked and then wiped to remove excess ink, leaving only the ink contained within the hardened gelatin. The image is then transferred onto a dampened sheet of paper under pressure. The result is a precise and continuous tonal reproduction of the original photograph with exceptional detail and clarity.
Collotype printing was particularly popular in the late 19th and early 20th centuries for reproducing fine art photographs, as it allowed for a faithful replication of the nuanced tonal values and textures present in the original artwork. However, the process is labor-intensive and requires considerable skill, leading to its decline in popularity after the advent of more economical and automated printing technologies. Nonetheless, collotype remains highly regarded among fine art printers and collectors for its unique visual qualities.
The word "collotype" was coined in the 19th century and is derived from two Greek words: "kolla" meaning glue or gum, and "typos" meaning impression or print. The term essentially describes the nature of the printing process involved in collotype.