Photography: A Mini-History


 

1839 was an important year in the history of record-keeping. It was in this year that the first practical form of photography, the Daguerreotype, was invented. Without this invention almost 170 years ago, PhillyHistory.org would not have been possible. Most of the images on this website come from one of three photographic types: the negative, the print, and the digital photograph. The majority of these, however, come from the incredibly large collection of negatives in the city’s possession.

Not all photographic negatives, however, were created the same. Over the short history of this medium, there have many different types of both negatives and photographs, especially in the first few decades after 1839 when photography was in its infancy. The first of these forms that could be used in a practical manner, the Daguerreotype, was introduced by Louis Jacques Mande Daguerre.

Although Daguerre’s was the first practical method of photography developed, there were successful earlier attempts. For example, in 1826 Nicephore Niepce invented what he called a “heliograph.” He took a photograph of his courtyard by exposing a sheet of pewter covered in light sensitive materials, using sunlight as his only light source. However, this process took over 8 hours to complete, making it much less practical to use as a method of record keeping than the much faster Daguerre method. (To read more about Niepce’s first photograph, see the Nicephore Niepce website link in the references section of this blog).

Like Niepce’s process, the daguerreotype also consisted of an image created on a sheet of metal. In this case the medium was a copper plate coated with silver iodide. Unlike Niepce’s process, however, the photograph created was a direct positive image. These photos were the predecessors of the types of images added to PhillyHistory today.

The first negative/positive process was patented the same year as the daguerreotype by William Talbot. This process, or the Calbotype process, created a paper negative which could then produce a positive image (or multiple positive images) by placing the negative in direct contact with light-sensitive paper and exposing the paper to daylight. Slightly less than 20 years later, in 1855, glass negatives were introduced to the United States. These glass negatives were preferable to paper negatives as the image produced was of a much better quality. It was only with the introduction of the glass negative that the negative/positive process of making photographs began to replace direct positive processes such as the daguerreotype.

The earliest glass plate negatives were “wet plate” negatives. They were called “wet plate” because this process required the photographer to coat a plate of glass with light sensitive materials, expose, and develop the photograph all before the coating dried. There was continued experimentation using various materials for emulsions (the emulsion is the layer of light sensitive material that is coated onto a base, for example glass, in which an image is formed when it is exposed to light). Some of the types of emulsions that were tried included albumen (a combination of sodium or ammonium chloride mixed with egg whites) and gelatin.

In the Philadelphia City Archives, the earliest forms of negative we scan for the PhillyHistory website are glass plate negatives. The above photograph, taken in 1894, is an image from one of these glass plate negatives. However, as is evidenced by the cracks visible in some of the other photographs on PhillyHistory, the glass negatives were found to be problematic, mainly because they are so incredibly fragile.

To help alleviate this problem, in 1887 George Eastman introduced cellulose nitrate film. This form of negative consisted of a nitrocellulose base and a gelatin emulsion. It was in use between 1913 and 1950. At the time, this was seen as an improvement over the glass negative, as it was much less fragile than its glass counterparts. However, today archivists have found this negative to be itself fragile as it ages. The nitrocellulose base is notoriously unstable as well as flammable, making it important to transfer the images on these to another medium (as, for example, scanning would accomplish) in order to preserve the information they contain.


 

Between 1937 and 1956 another film created by the Kodak company, safety film, was widely used. This film was made of cellulose diacetate and was found to be much less of a fire hazard. However, this film too has been found to be somewhat unstable. Over time, the cellulose diacetate shrinks as it deteriorates, causing wrinkles in the layer of emulsion, which does not shrink at the same rate. The photograph to the left is an example of this type of deterioration. In1947, Kodak introduced another type of safety film which is still in use today, which is made of a more stable material, cellulose triacetate.

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