Eight glass plate photographic prints. Presumed to date from Sir Joseph Swan's early experiments with dry plate photographic print techniques (approximately 1870s)
History of Swan's Development of Dry Plate Photography
One of the big problems for early photographers was that a glass plate had to be prepared with wet collodion only a very short time before exposure, and then after exposure had to be developed immediately. This was particularly inconvenient for photography outside of the studio – landscape photographers had to carry a dark tent and all of their equipment with them so that the plates could be prepared immediately before taking photographs, and then processed immediately after.
In the 1850s a new dry plate method was invented which could be prepared in advance of use, and then after use could also be stored and developed later. This was a significant step in making photography an easier and more practical process, and dry plates were manufactured from 1857. Nevertheless uptake was slow. Their big disadvantage was that they required extremely long exposure times, so wet plates continued to be used for a further twenty years.
In the 1870s however, whilst working with wet plates, Swan noticed that heat increased the sensitivity of the silver bromide emulsion. He started to experiment with dry plates, developing a ‘cooking’ technique, and by 1877 Mawson and Swan were manufacturing dry plates with exposure times of 1/20th of that of collodion plates.
Now, plates could be prepared in advance, stored until the photographer had returned to their dark room, and developed with relative ease. It revolutionised landscape photography and heralded the beginnings of the hobby photographer.