At the beginning of the nineteenth century, the primitive technology required to make photographs as we now know them was already in place. All it needed was to bring the various component parts together to make the whole process possible.
Artists had been using the camera obscura and the camera lucida to project images on to a flat plane via a simple lens. The Italian painter Canaletto used this principle to enhance the perspectives of his paintings of Venice.
It was also known that certain compounds of silver darkened when exposed for a period of time to sunlight. What in fact happened was that they reverted back to microscopically small particles of metallic silver. All that was needed was to find a way of bringing these together in order to fix a projected image on to readily available material. And, incidentally, to find a word to describe this new science.
For a painter the obvious choice of material on which to present this image would have been a piece of primed canvas. As it happened this was never considered an avenue worth pursuing although very early experiments had been made with leather as a potential medium. An artist using watercolours or pencil drawings would have been more inclined to favour paper. At the time the only means of reproducing images on paper was by engraving a copper plate or a wooden block or by etching a steel or zinc plate with acid and, having rubbed them with ink, pass them in contact with a sheet of paper through a heavy roller press to transfer the ink from the plate or block onto the paper. Thus the only alternative choice of a medium for the photographic process was a copper or zinc plate. The decision as to which method to use was crucial to the evolution of photography. The two main protagonists in what later became at times a bitter struggle to dominate a potentially unlimited commercial market were the French and the British. The French put all their efforts into working with metal plates. Niepce used a zinc plate coated with a substance known to lithographers as Bitumen of Judea, whereas Daguerre preferred to experiment with a copper plate coated with silver. Both of these produced a negative which, when turned at a certain angle to the light would appear as a positive.
The advantage of this method was its relatively 'instant' quality. In a very short time you could have a real picture of yourself or your family without the expense and the tedium of a sitting for a painter. Daguerre took his new invention to America where it became an immediate success. However its limitations were serious enough to render the French process obsolete within less than twenty years after its introduction. The great disadvantage of Daguerre's images was that they were 'one-offs' and could not be reproduced in large numbers as etchings or engravings could be. They were small and enclosed in an elaborate gilt and leather case, more suitable for standing on a mantel shelf than for hanging in a frame on a wall. Their production involved at one stage holding them over mercury vapour which in the primitive conditions of the time was a very hazardous procedure. It is still as dangerous now, which is why there is no chapter in this manual entitled 'Making a Daguerreotype'.
At this point Fox Talbot entered the arena. An indifferent draughtsman and water-colourist, his main concern was to fix an image mechanically onto paper. His invention of the Calotype and the salt print gave us the negative positive process which became the the basis of photographic printing which is still used today. In fact there has been relatively little radical change in silver printing methods since his time. Salt prints were modified to produce albumen prints which were common currency for much of the nineteenth century. Silver bromide printing took over from albumen, and with an increase in printing speed it was possible to make enlargements by projection in an enlarger. Finally, in the middle of the 20th century, resin coated and variable contrast papers were introduced. The real technical advances were made in the field of negative making. Paper negatives gave way to wet glass plates which were followed by dry plates, followed by flexible roll films and cine films for miniature cameras. Finally colour slides and colour negatives completed the picture.
Most of the alternative methods described in this manual were introduced for a variety of reasons. Some were developed as commercial alternatives to the predominant albumen print, or for greater permanence (carbon and platinum). Some appeared as a result of the various 'art' movements at the turn of the century (gum and bromoil). And some were brought in to satisfy the demand for photographs to be reproduced on the printed page (photo etching and photogravure) to replace the hand engraved plates taken from photographs which filled the pages of magazines, newspapers and books.