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How Does a Daguerreotype Work?

By Contributor ; Updated September 21, 2017
Yale Collection of American Literature, Beinecke Rare Book and Manuscript Library

What is a daguerreotype?

A daguerreotype is a photograph made inside a camera without using a negative. The resulting picture is a one of a kind image created by exposing a copper plate to a chemical process. Invented in France by Louis Jacques Mandé Daguerre in 1839, daguerreotypes were the first type of photographic images ever made, and they are known for their clarity and sharpness.


Daguerreotypes are made with sheets of silver-plated copper. The first step to create a daguerreotype is to clean and polish the copper plate until it shines like a mirror. Place the plate in a light-sensitive box and expose the plate to iodine. The vapors from the iodine create a light-sensitive coating on the plate. The plate is then transferred to a sliding box camera. Exposure begins when the lens cap is removed. Exposure times can take anywhere from 1 to 20 minutes, depending on what type of camera is used. After exposure, the plate is developed over mercury heated to 75 degrees until an image appears. The plate is then immersed in warm saltwater, rinsed with water and toned with gold chloride. After being developed, daguerreotypes are often put under glass to protect the image.


Though daguerreotypes are clearer and more detailed than standard photographs, viewing them correctly can be tricky. The silver coating on the plate acts like a mirror, and when viewed at certain angles the picture can look like a negative image. Daguerreotypes must be viewed straight on to avoid this. The images on daguerreotypes are also laterally reversed, reflecting a mirror image of the person or scene in the photograph. Wedding rings appear on people's right hands, and any text in the photo will appear backwards. Long exposure times also make daguerreotypes difficult. People being photographed must stay still for a long period of time to reduce blur in the image. Another drawback to creating daguerreotypes is that the chemicals used to create them--specifically mercury--are highly toxic. Finally, daguerreotypes are fragile and prone to tarnishing. They must be handled gently and kept under glass and out of direct sunlight.

The Image

Because there is no negative used to create a daguerreotype, there is no "grain" in the image. The resulting photo is almost as sharp and detailed as real life. If you look at a daguerreotype with a magnifying glass, you can see hair, jewelry and small background details in crisp focus. It is also difficult to successfully copy a daguerreotype, so the image on the plate is unique.


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