Louis Daguerre developed the daguerreotype, the first publicly announced photographic process, in 1839.
A daguerreotype formed an image directly on a silver-plated copper plate. The plate was polished, sensitized with iodine vapour, exposed in a camera, developed with mercury vapour, and fixed so the image would not continue changing. The result was a highly detailed one-of-a-kind photograph.
Daguerre’s work built on experiments by Joseph Nicéphore Niépce, with whom he had formed a partnership. After Niépce died, Daguerre continued improving the process and reached an agreement with the French government. The process was publicly announced in Paris in 1839.
A daguerreotype was not a paper negative that could produce many copies. That feature distinguishes it from William Henry Fox Talbot’s calotype process. Daguerreotypes were valued for sharp detail but required long exposures and careful handling of toxic chemicals.