Silver Nitrate: Cornerstone of Photography

By Fabian Toulouse

While it is accepted that the first photograph was probably taken earlier, the official invention of photography was made in 1839 by French artist and chemist Louis J.M. Daguerre. In partnership with Joseph Nicphore Nipce, they expanded upon a discovery made by Johann Heinrich Schultz in 1724 regarding how a certain silver nitrate and chalk mixture darkened when exposed to light. The daguerreotype, or earliest type of photograph, was born.

Daguerreotypes are actually negative images that are exposed onto a mirror-polished surface of metal that has been coated with iodine-soaked, silver halide particles. In latter developments iodine was replaced by bromine and chlorine vapors, which allowed for shorter exposure times. This direct photographic process did not allow for the duplication of the image, however.

In America, in 1839, Robert Cornelius worked with his father in silver plating and metal polishing. After being approached by Joseph Saxton, Cornelius moved into the young field of photography, using his mastery of chemistry and metallurgy to make a daguerreotype and turn it into the first photograph. It was a self portrait and the first human portrait to be produced. Cornelius ran two photographic studios in America in 1839 and 1843 until he eventually rethought his commitment and returned to his family's gas and lighting company.

Silver nitrate is an easily reproduced compound that has become the foundation of photography. 1841 saw Englishman, William Henry Fox Talbot introduce a new process that involved sensitized paper that contained a coating of silver iodide which produced a negative image when exposed to light. The paper was semi-transparent, which could be laid over sensitized paper to produce a positive image or direct copy of the original.

Originally, silver halide, formed through the reaction of halide and silver nitrate, was diluted in a solution of gelatin which was bound and carefully controlled. Gelatin was an vast improvement over the previously used egg whites which produced sharp images but were easily damaged. In later upgrades, Dr. R.L. Maddox solved this problem by figuring out a way to prepare gelatin dispersions of silver salts on glass plates.

In 1887, George Eastman prominently introduced the Kodak system, wherein a silver halide-in-gelatin dispersion was coated on a silver nitrate base and then loaded into a camera. With this system, a person could take up to 100 pictures at a time. When they were all exposed, the person simply returned everything - camera and film, to be processed in Rochester, New York and modern photography was born.

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