What is Wet Plate Collodion?

This process was invented in England by Frederic Scott Archer in 1851. He was a sculptor who wished to make a visual record of his works. He did not patent the process, but gave it to the then very small photographic community. He does not appear to have been successful as a sculptor, and died a pauper. He is buried in Kensal Green Cemetery in London.

His invention made it easy to create copies of images, and swiftly overtook Daguerreotypes as the process of choice. The images are made on either glass, known as ambrotypes, or thin sheets of metal, known as tintypes.

The plate is covered with collodion (a mixture of ether, alcohol and guncotton) which is then, in a darkroom, sensitized in a bath of silver nitrate solution. The plate is then put in a light-tight holder.

Once the holder is placed in the camera the holder is opened and the photographer then opens the lens for an appropriate time.

The plate has to be wet throughout this process, which means it has to be completed within about 15 minutes.

The exposure could take 10 minutes or longer, so photographers used neck braces to hold the subject’s head still. With modern chemicals and bright lights, or natural sun, exposures can now be made in a few seconds but head braces help ensure focus.

The plate is then developed and fixed. Once dry, it is coated in clear varnish or similar to prevent the silver tarnishing.

The ambrotype images, which are made on glass, are set against a black background so that they do not appear as negatives. It was because the glass plates appear as negatives that it was so easy for copies to be made.