Collodion process

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Collodion process

The collodion process is an early photographic process that was widely used in the mid-19th century. It was invented by Frederick Scott Archer in 1851 and quickly became popular due to its ability to produce detailed and stable images. The process involves coating a glass plate with a solution of collodion (cellulose nitrate) and then sensitizing it with a solution of silver nitrate. The plate is then exposed in a camera while still wet, developed, and fixed to create a photograph.

History

The collodion process was introduced as an improvement over the earlier daguerreotype and calotype processes. The daguerreotype, invented by Louis Daguerre, produced highly detailed images but was expensive and not easily reproducible. The calotype, developed by William Henry Fox Talbot, allowed for multiple copies but lacked the sharpness of the daguerreotype. The collodion process combined the best features of both, offering sharp images and the ability to produce multiple copies.

Process

The collodion process involves several steps:

1. Preparation of the Plate: A glass plate is cleaned thoroughly and then coated with a solution of collodion. The collodion contains cellulose nitrate dissolved in a mixture of ether and alcohol.
2. Sensitization: The collodion-coated plate is immersed in a solution of silver nitrate, making it sensitive to light.
3. Exposure: The sensitized plate is placed in a camera and exposed to light. The exposure time can vary from a few seconds to several minutes, depending on the lighting conditions.
4. Development: The exposed plate is developed by pouring a solution of pyrogallic acid or ferrous sulfate over it. This step reveals the latent image.
5. Fixing: The developed image is fixed using a solution of sodium thiosulfate or potassium cyanide, which makes the image permanent.
6. Washing and Varnishing: The fixed plate is washed to remove any remaining chemicals and then varnished to protect the image.

Types of Collodion Photographs

There are several types of photographs that can be produced using the collodion process:

• Ambrotype: A positive image on glass, created by backing a collodion negative with a dark material.
• Tintype: A positive image on a thin sheet of metal, usually iron, coated with a dark lacquer or enamel.
• Negative: A glass plate negative that can be used to produce multiple positive prints on albumen paper or other photographic papers.

Advantages and Disadvantages

The collodion process had several advantages over earlier photographic methods:

• Sharpness: The process produced images with exceptional detail and clarity.
• Reproducibility: Unlike daguerreotypes, collodion negatives could be used to make multiple positive prints.
• Cost: The materials used in the collodion process were less expensive than those used in daguerreotypes.

However, the process also had some disadvantages:

• Complexity: The process was labor-intensive and required a portable darkroom for fieldwork.
• Sensitivity: The plates had to be exposed and developed while still wet, limiting the time available for these steps.

Legacy

The collodion process was eventually replaced by the gelatin silver process in the late 19th century, which was more convenient and allowed for dry plate photography. However, the collodion process is still used today by some photographers and artists who appreciate its unique aesthetic qualities.

Related Pages

• Frederick Scott Archer
• Daguerreotype
• Calotype
• Albumen print
• Gelatin silver process