Pascall’s Patent Expanding Ridge
Cristoid film, developed by John Tyack Sandell, had two layers of emulsion of different sensitivity, coated on a hardened gelatine base. The films were available as sheets or roll-film.
John Tyack Sandell was born in Somerset, England on 29th September, 1853. In 1871 Sandell was an apprentice chemist in Somerset, England. He became a chemist by trade and, after his apprenticeship, was employed by R. W. Thomas and Company.
After being promoted to general manager at R. W. Thomas and Company, John Tyack Sandell became the guiding force behind the lantern plate known as “the Thomas plates.” Encouraged by this success, he developed his own line of double-film and triple-film plates that were manufactured by a company that bore his name, Sandell Dry Plates and Films Ltd., based in South Norwood.
Sandell was most comfortable either inside his laboratory or outside taking landscape photographs. His photographs of the Pharmaceutical Society were exhibited on his multi-coated plates.
Sandell received a patent for his cristoid film, which was marketed shortly thereafter in December 1899. A sheet constructed of hardened gelatin, it needed no support from glass or plastic. A fast and light-sensitive silver gelatin emulsion was superimposed onto a slow, thick, and comparatively insensitive emulsion. The result was a flat film that was considerably more opaque than its celluloid roll film counterpart.
Highly protective of his plates, Sandell marketed them and demonstrated their preparation to the public personally. However, despite their perfection, his plates never achieved the commercial success they deserved because their development took more time and required greater technical precision than their easier and less expensive counterparts.
Like most visionaries, Sandell proved to be a poor businessman. His association with Sandell Films and Plates ended badly in 1902, and shortly thereafter his health began failing rapidly. He died virtually penniless on December 29, 1906.