A unique portrait shoot of A. Lange & Söhne

In a first step, a glass plate is coated with collodion, a liquid photosensitive base. This is made by dissolving cellulose nitrate in ether and alcohol and subsequently adding a soluble iodide. Around a dozen different chemicals are used in the process before the finished image can be seen.

In the darkroom, the coated plate is dipped into a dish containing silver nitrate solution. In this phase, the iodine salts are chemically replaced by light-sensitive silver iodide and silver bromide particles that are evenly distributed in the collodion coating. The wet plate prepared in this way is placed in a light-tight plate holder and slid into the camera.

The low sensitivity of 1 to 2 ASA demands exposure times of several minutes or an extremely strong source of light. Exposing the plate to light initiates a chemical reaction in the light- sensitive coating, the results of which first slowly appear in a developing bath in the red light of the darkroom.

As the process only works while the plate is still wet, the exposed plate must be developed immediately. If the plate dries out, the enormous effort is wasted. Depending on the ambient temperature, the photographer must complete the entire process from coating the plate to developing the final image within a period of only five to fifteen minutes.

After developing, the images must be fixed, watered and dried before they can be coated and made ready for subsequent scanning. The effort involved is amply rewarded. The results are unique and almost magical photographs with impressive contrast and brightness that seem to be from another age.