Wet Plate Collodion
A Brief History
Frederick Scott Archer
Wet Plate Collodion is an early photographic process, said to have been invented, almost simultaneously by Frederick Scott Archer and Gustave Le Gray in the late 1840's. Archer is generally credited with it's invention, having published the process in ‘The Chemist’ in March 1851. Archer did not patent his collodion process and died impoverished a few years later (1857). During the subsequent decades of its popularity, many photographers and experimenters refined or varied the process. By the end of the 1850s it had almost entirely replaced the first practical photographic process, the daguerreotype. Wet plate collodion is also the same process that was used to document the United States civil war in the 1860s by Matthew Brady and his band of photographers.
The process involves coating a plate of glass or metal with collodion (a mixture of raw cotton, which has been treated with nitric and sulfuric acids, dissolved in ether and alcohol, with a little iodide and bromide mixed in) to create a sticky, skin-like surface (binder) and then sensitizing the plate to light with a mixture of water, silver and salt. The plate is then exposed to light, developed, fixed, washed, dried and finally varnished for longevity. Many people recognize wet plate collodion as 'tintype', though original tintypes were actually not made on tin at all, but thin sheets of iron. Wet plate collodion can also be made on glass as a negative. The negative is often placed on a black sheet of paper or velvet to create a positive image.
During the 1880s the collodion process, in turn, was largely replaced by gelatin dry plates—glass plates with a photographic emulsion of silver halides suspended in gelatin. The dry gelatin emulsion was not only more convenient but could be made much more sensitive, greatly reducing exposure times.
One collodion process, the tintype, was still in limited use for casual portraiture by some itinerant and amusement park photographers as late as the 1930s, and the wet plate collodion process was still in use in the printing industry in the 1960s for line and tone work (mostly printed material involving black type against a white background) as for large work it was much cheaper than gelatin film.
(details of the process can be seen below.)
"I have seized the light. I have arrested its flight."
- Louis Daguerre-
The wet plate collodion process was (and is) a very challenging one, requiring immediate access to a darkroom space. From sensitizing the plate to the final, processed image, the plate must not dry or it will loose its sensitivity.
The photographer pours collodion (which is a mixture of collodion USP, ether and salt) on the plate (usually glass or metal) and runs the excess off into a second bottle.
Sensitizing the Plate
When the collodion becomes slightly tacky, the plate is placed into a bath of silver (under safelight) that has been dissolved in distilled water. This solution is traditionally stored in a tank or box. The plate becomes light sensitive at this point.
Loading & Exposing
After 3-5 minutes the plate is removed from the silver box under safelight and placed into a holder that goes into the back of the camera. An exposure is made. The exposure time varies greatly depending on the age/quality of the formula and the light source itself.
Developing & Fixing
The plate is then removed from the holder (again under safe light), developed, fixed and washed much like a traditional darkroom print. Development times are usually very short (less than 30 seconds).
Washing and Varnishing
The plate is then washed thoroughly to remove all excess fixer. To protect the delicate image, the photographer applies a coat of varnish to the plate. Application is conducted in much the same way that the collodion was applied to the plate.
First, the photographer heats the plate over a flame. Heating the plate helps the varnish to level off and makes the vanish cover more evenly. The photographer then pours the varnish onto the emulsion side of the plate, tilting the plate until it is fully covered and pours the excess back into the bottle. The plate is then allowed to dry. Once completely dry, the plate is ready to be framed and displayed.