Daguerreotype
Invented by Louis-Jacques-Mandé Daguerre and introduced worldwide in 1839, daguerreotype was almost completely superseded by 1860 with new, less expensive processes yielding more readily viewable images. In the late 20th century, there was a revival of daguerreotypy by a small number of photographers interested in making artistic use of early photographic processes.
Louis Désiré Blanquart-Evrard
He was born and raised in Lille where he studied chemistry with Charles Frédéric Kuhlmann and miniature painting on porcelain. After Louis Daguerre solved the problem of long exposure time and introduced daguerreotypy, a practical photographic process, to the general public in 1839, Blanquart-Evrard developed interest in photography. He studied the "calotype", salt-print negative process, and in 1847 became the first person to publish on negative/positive paper photo process in France. He developed a method of bathing the paper in solutions of potassium iodide and silver nitrate rather than brushing these chemical baths on the surface. In January 1847, he presented his research on stabilizing the photo prints by floating them in the silver solution to the French Academy of Sciences.