Daguerreotype is a type of early photography. It was named after its inventor Louis Jacques-Mandé Daguerre and it was the first photographic process to come into wider use. Methods used before were experimental and not too efficient. Daguerreotypes are on bright, mirror-like surfaces of metallic silver and can be positive or negative, depending on the lighting conditions.
Daguerreotype, as many other discoveries, didn’t appear out of nowhere. Earliest mechanical methods of capturing visual scenes appeared in Renaissance. Artists of that time used camera obscura to sketch what they wanted to paint. Camera obscura will later be used in photography. Albertus Magnus, alchemist and astronomer, discovered photosensitive substance silver nitrate in the 13th century. Johann Heinrich Schulze discovered another photosensitive substance, a silver and chalk mixture, in 1724. Nicéphore Niépce discovered bitumen-based heliography in 1822. In 1829, Chevalier, who supplied lenses for cameras obscura of both Niépce and Daguerre, introduced them to each other and then their partnership begins. Niépce's at first tried to reproduce prints and drawings for lithography. He used bitumen of Judea (asphalt) which hardened differently, depending on how much it was lightened. His images needed exposure of 8 hour to produce the picture. After that they were washed in oil of lavender which left a relief image. When Niépce died in 1833, Daguerre continued his work and switched from bitumen to copper plates coated with iodized silver. His first tries also needed a long time of exposure but in 1935 he found (accidentally) that mercury can develop plates that were exposed for only 20 to 30 minutes. He further improved this technique by discovering a method to prevent further overexposure of daguerreotype by fixing the picture in a strong solution of table salt. Daguerre gave his process to the French government in exchange for a lifetime pension. French government gave daguerreotype "free to the world" on August 19, 1839. This was a popular method of making photographs until early 1860s. Processes invented at that time were cheaper and less complex. Because of that they almost entirely replaced daguerreotype as a method of photography. During the 1980s and 1990s small number of photographers tried to revive daguerreotype as an interesting method and they still use it even today.
Daguerreotype was a complex process which consisted of these steps:
First step was manufacturing of plates. Base of the plate was copper or brass and it was covered with silver (pure preferably). This was done in two ways: silver was heat-fused onto the top of a thick copper ingot or a layer of pure silver was electroplated onto a bare sheet. In a case of heat-fusion, fused plates were then rolled under pressure to produce thin sheets. These plates were polished before use to remove tarnish and other contaminations. For polishing were used rottenstone (fine powdered porous rock), hide, velvet, jeweler's rouge (ferric oxide), and lampblack. As a final step in polishing, plate was swabbed in nitric acid which removed any residual organic matter. After polishing, plate was covered with halogen fumes in a process called sensitization. This turned silver surface into silver iodide. Halogen fumes were later replaced by bromine fumes which made surface more photosensitive. Plate that is prepared like this was placed in camera and exposed. This produced an invisible latent image on the plate. After the exposure is over, plate was removed from the camera while protected from light. Plate is then exposed to the mercury fumes which develop the image and make it stronger. Remaining silver iodide is removed with a solution of salt and with that image is fixed. Picture is then sealed with a protective cover glass because it can be easily tarnished from exposure to the air.