Questions & Answers


First formulated in 1846, collodion was, and still is, used as a
medical dressing. Made from cotton (or cellulose),
soaked in nitric and sulphuric acids,
it is thoroughly washed and dried,
and then dissolved in ether and alcohol.

The American Heritage Dictionary defines collodion as follows: col.lo.di.on (ke-lo' de-en) n . a highly flammable, colorless or yellowish syrupy solution of pyroxylin, ether and alcohol, used as an adhesive to close small wounds and for photographic plates, from the Greek, kollodes, glutinous, glue like

When allowed to dry it left a clear, thin, tough flexible coating. In 1851 Frederick Scott Archer found it to be a perfect vehicle to hold light sensitive chemicals on glass and later a wide variety of surfaces including asphalted iron for making ferrotypes, popularly called tintypes. A positive image on glass, called an ambrotype; a positive image on asphalted iron, called a "tintype" or ferrotype; and a negative, can all be made using the wet-plate collodion process. Also called "cellulose nitrate," this is similar to the base used later for making movie films.

A daguerreotype is a positive, unique image made on silver-plated copper. It is unique because it is the same plate that was in the camera, there is no negative. Daguerreotypes were invented by Louis Jacques Mande Daguerre, announced in 1839, and were popular until the mid 1850s. An ambrotype is a wet-plate collodion positive image made on glass, also one of a kind. Ambrotypes were popular from 1852 to the mid 1860s. A quick way to tell the difference is that a daguerreotype looks mirror-like, and in certain angles, you can see yourself. This is never true with an ambrotype.



Click here to read a reprint from The Collodion Journal.



1. Collodion, containing small amounts of iodides and bromides, is poured onto a scrupulously clean piece of clear glass to produce an even coating. The collodion is allowed to flow to all four corners of the plate and care must be taken not to double coat areas or ridges may form in the final negative. The excess is poured off the plate and back into the bottle.
2. Before the ether and alcohol evaporates from the collodion, the plate is taken to the darkroom (with a red window) and dipped into a solution of silver nitrate, where it remains for at least four minutes. At this time the silver nitrate bonds with the iodides and bromides in the collodion to make a light sensitive film of silver halides on the surface. While the plate is in the silver nitrate, the camera is set up and focused on the subject.

3. The light sensitive plate is placed into a light proof holder and taken to the camera. The plate is wet and silver nitrate drips from the holder.
4. The camera, which has been trained on the subject and focused, receives the plate holder. A "dark slide" is removed to expose the plate to the inside of the camera. Exposure is made by removing the lens cap and the time is counted. It takes from 20 seconds to 5 minutes to make the proper exposure for a wet-plate negative depending on the age of the collodion and the quality of light on the subject.
5. The plate holder is secured, removed from the camera and brought back to the darkroom. The plate is removed from the holder and the developer, a solution of iron sulfate, acetic acid and alcohol is poured onto the collodion side. The image becomes visible within a few seconds as the areas struck by light in the camera turn to metallic silver. When development is complete the developer is removed by a wash of clean water. The plate can now be safely taken from the dark room.
6. The developed plate is taken from the darkroom and place into a tray of sodium thiosulfate (called sodium hyposulphate in the wet-plate era and fixer in modern terms) to remove the unused silver halides and then washed in fresh water.

7. Using an alcohol lamp the plate is dried and while still warm, flowed with a protective varnish made from gum sandarac, alcohol and oil of lavender. The sandarac varnish is extremely sticky until thoroughly dried.

The plate is now a negative and can be used to make a wide variety of paper prints. Collodion plates have the finest grain of any silver based film and can be enlarged to make very big prints without loss of detail. The blurred areas in collodion negatives are either a result of subject movement or early lens designs.

One-of-a-kind positive images, such as ambrotypes or tintypes are made nearly the same way. Positives require much less exposure time, and sometimes, other formulas are used; for example in the collodion the photographer might have used potassium bromide instead of cadmium bromide, and potassium cyanide was usually the preferred method for fixing collodion positives.

Whether making positives or negatives, from the time the plate is coated with collodion to the development, the collodion must remain wet or the plate loses sensitivity. This is why the technique is called the wet-plate collodion method. Now that you know about some of the challenges facing wet-plate photographers, imagine what it took to travel with collodion...? When gelatin dry-plates were invented in the 1880s, many photographers gave up their portable darkrooms for a more "user friendly" method.

Mark Osterman &
France Scully Osterman

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