Photographic Chemistry: The Beginnings Of Photography

November 3, 2021

It has been more than 180 years since the precursor of one of the most outstanding inventions of the last decade was presented. On August 19, 1839, Luis Daguerre presented his latest invention to the French Academy of Sciences: the daguerreotype. This allowed to capture an image through a chemical process. That day the daguerreotype patent was also released, leading to the development of photography.

Quick History of Photography

The first photographic or heliographic procedure was invented by Joseph Nicéphore Niépce around 1824. The images were obtained with Judean bitumen, spread on a silver plate, after an exposure time of several days. In 1829, Niépce associated Louis Jacques Mandé Daguerre in his research.

In 1832, a second procedure was developed from the residue of the lavender oil distillation, which produced images with an exposure time of a whole day. Niépce died in 1833.

Daguerre continued working alone and invented, in 1838, the daguerreotype, the first procedure that included a development stage. The silver plate covered with a thin layer of silver iodide was exposed in the dark chamber and then subjected to the action of mercury vapors. This caused the appearance of the invisible latent image, formed in the course of exposure to light.

This development consisted of a great amplification of the effect of light, with which the exposure time did not exceed 30 minutes. Fixing was obtained by immersion in water, saturated with sea salts.

In July 1839, another Frenchman, Hippolyte Bayard, discovered the means of obtaining positive images directly on paper. A paper coated with silver chloride was darkened in the light and then exposed in the dark chamber after being impregnated with silver iodide.

Chemical Processes in Photography

There are many important chemical reactions within the photographic process; such as those carried out during the manufacture of the emulsion, the development process, the bleaching process, the enhancers, the toning and color processes.

In the year 1727 Johan H. Schulze (1687-1744), experimented with silver nitrate and its reaction to light; discovering that silver nitrate was blackened by the action of light. By 1800 Thomas Wedgewood (1771 – 1805) and Humpry Davy (1778 – 1829) applied this principle to achieve the registration of images by action of light, however; these images were not permanent.

Silver Photography

Some silver elements are an important part of photography, because in the course of its refinement, many silver-based substances were used to generate the correct images. As with the daguerreotype, the latent image was then revealed, by means of a chemical, the developer: a solution of gallic acid and silver nitrate.

In 1841, the physicist Fizeau used silver bromide, whose sensitivity to light is far superior. Nothing more than a few seconds of exposure was enough to obtain a daguerreotype. So taking portraits became possible.

Current Analog Photography

The current photographic emulsion contains silver halide crystals, the most commonly used is silver bromide (AgBr), however, there are also emulsions of chloride, iodide or mixtures between them. This crystalline form of silver halides in photography is known as the emulsion grain, they have varied sizes, from the very small (less than one micron), to those of a few microns.

The size of these grains gives the material its sensitivity characteristic, which is set in ISO degrees. These grains are suspended in a thin layer of gelatin that will be applied to a support such as paper.

It works as a stabilizing colloid, in its liquid form it does not allow the silver halides to precipitate out of the solution favoring their uniform distribution.

The history of photography is wide, huge and full of chemical experiments, which today are not essential, since we all have digital cameras in our smartphone, but if you want to take photos in the traditional style, you know that these procedures still exist.

Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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