William Henry Fox Talbot was an English scientist and scholar in the early 1800’s. Although he was a contemporary of Daguerre, his contributions to photography were independent of what was going on with Daguerre and in mainland Europe. In 1834, Talbot was able to create a different camera based image process that utilized the photosensitivity of silver salts, called the salted paper print.
In a salted paper print, Talbot took ordinary paper and coated it with sodium chloride, let it dry, then recoated it with silver nitrate. The result was silver chloride, which proved more light sensitive than silver chloride and allowed him to decrease his exposure time. The way he exposed the paper with tiny cameras was a “printing out” process, meaning the image was directly exposed on the paper, and the paper darkened when exposed to light meaning the image was created without exposure to chemicals. There was no “emulsion” or “development” as is the case today. He “fixed” the images with potassium iodide, but ultimately, these images were “negatives” and Talbot wanted to get “positives”.
It’s interesting to note that Talbot’s wife, Constance, also participated in image making with Talbot, thus making her the first known woman photographer.
As a scientist, Talbot used his skills to come up with a way to turn the negatives into positives by contact printing. He placed another coated piece of paper underneath the original and exposed it to light. The darker, negative areas blocked light coming through to the bottom sheet, while the originally light areas, darkened the bottom sheet, thus a reversal in image. He called this process a “photogenic drawing”. The only downside was he still wasn’t able to gain the detail he craved out of the images.
Talbot continued to work on improving his process. Much like other things we’ve seen already, Talbot’s discovery came by accident. Apparently, he had brushed a piece of paper with gallic acid, prior to exposure, then exposed an image that appeared to not have “worked”. The paper was blank. When he came back later, the image had appeared and Talbot concluded the gallic acid had acted as a developer. He refined the process and eventually developed the following procedure:
- Take an exposed sheet of iodized paper to the darkroom and brush it with gallic acid.
- As it’s brushed with gallic acid a negative appears on the paper.
- The paper is contact printed onto unexposed, salted paper (using the sun, there were still no enlargers at this time), thus resulting in a positive.
Ultimately, Talbot coined the term “Calotype” (beautiful print in Greek) for this process. What is most important to take from this process is that it was the first time photography was formally structured into a two-part printing process. It began with a negative, from which an infinite number of positive copies could be made. All silver based photographic printing processes are based on this same concept, even still, today.
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