Collodion wet plate negatives

Gelatin dry plate negatives

Albumen silver photographs

COLLODION WET PLATE NEGATIVES

Wet-collodion-on-glass negatives were the most common way to produce a negative between 1855 and about 1881. The process was first published in 1851 by F. Scott Archer. It was a complex and extremely time consuming process. Like other photographers, Captain Sweet had to create each negative just before it was required for use as the process only worked while the emulsion on the negative was still wet. For a landscape photographer this meant transporting all of the necessary equipment (including a dark tent, chemicals and glass plates) to the location. The only parts of the process which could be completed in advance were the preparation of the glass and the making of the collodion. First, a glass plate had to be cut to the correct size for the camera. In Sweet's case, this was 7 7/8" x 10 5/8". The collodion could be made in the studio by dissolving pyroxyline (gun-cotton) in one part alcohol and two parts ether. This mixture was allowed to stand for 24 hours in a bottle, after which the clear liquid collodion was poured into another bottle, leaving behind the sediment. The collodion became the vehicle for the sensitive photographic material, the first of which was an iodide, such as potassium iodide, which was dissolved in the collodion. A clean, smooth glass plate was then coated with the iodide/collodion mixture. As the plate dried the ether and alcohol evaporated, leaving a coating of pyroxyline mingled with iodide. The rest of the process had to be completed just before the negative was used.

Once Sweet had selected his view and set up his camera and equipment, he would sensitise the plate inside his dark tent by dipping it into a solution of silver nitrate. With the plate still wet he placed it in a negative holder - a small wooden box which kept the light out until the negative was placed into the camera. The glass plate was inserted into the camera in it's holder and exposed for 10 - 20 seconds, depending on the lighting conditions. Sweet returned the plate in its holder to the dark tent, making sure that no further light reached the negative. At this stage the image was still latent.

Sweet then developed the plate in the darktent where he had set up his trays, water and chemicals. First he dissolved the developer in water. The developer could be pyrogallic acid, gallic acid or proto-sulphate of iron. He poured the developer solution over the emulsion side of the glass plate and the negative image began to appear. Once the image had darkened to the desired amount Sweet washed the plate by plunging it into water to remove all the soluble substances. The image was then fixed by plunging it into a fixing solution, such as cyanide of potassium, which dissolved the semi-opaque coatings of iodide of silver. He then washed the plate in a current of cold water and dried it on a rack in the air. The negative could then be taken back to the studio for printing.

This brief explanation of the collodion wet plate process only gives the bare-bones of the steps to create a negative. In order to create a good collodion negative there were many other subtleties and details for a photographer to master. A detailed account of the process was published by Désiré van Monckhoven in his Popular treatise on photography in 1863. His treatise is available at albumen.stanford.edu.

© Karen Magee 2008 - 2009