Wet-plate photography and the collodion development process gradually replaced the daguerreotype as the primary photographic process from the 1850s through the 1880s, when much more convenient cameras became available. Even now, wet-plate exposures are difficult to perfect, and the process can take several minutes per each image, which must be captured and then developed and fixed all within several minutes before the wet plate dries. Wet plates are used with large-format cameras, and as you can imagine, the process of taking a single image at a time forces photographers to perfect their compositional skills, especially as the scene can’t be viewed through the lens while exposing a wet plate.
These downsides are quite the luxury in today’s immediate digital environment but, of course, that’s one of the principal reasons why wet-plate photography is seeing renewed popularity. The glass plates and unique collodion development process produce images of uncommon beauty, with rich contrast and an antiquated aesthetic, even when working with modern subject matter and contemporary models. The large glass plates provide almost grainless resolution, and while some practice will give you an understanding of the collodion process, the results also can be very unpredictable, with fun Holga-esque light leaks, interesting solarization effects and atmospheric one-of-a-kind artifacts from the rapidly drying emulsions.
Wet-plate photographs present a particular challenge in that images must be developed before they dry. Images are captured by directly exposing the projected image from the lens to a flat piece of glass, known as an ambrotype, or to a metal substrate like steel or aluminum, most often called tintype (though tin isn’t used). The plates are covered with light-sensitive chemicals immediately prior to the exposure, as well, and ironically, it’s often simpler to bring the darkroom to the location rather than taking the exposure and developing it in a darkroom, which would limit wet-plate photography to a studio. Los Angeles photographer Ian Ruhter converted a truck into a mobile wet-plate darkroom where he’s able to capture projections to five-foot wet plates. Whether working with modern cameras or more antiquated models, there are actually a number of modern photographers working with the wet-plate medium on everything from celebrity portraiture to fine art to nudes to Civil War reenactments, like Sally Mann, Ed Ross, Jill Enfield, Igor Vasiliadis, Luther Gerlach, Joni Sternbach, Mark and Kristen Sink, David Prifti and many others. A photographer based out of San Francisco named Michael Shindler even offers tintypes as a standard sit-down session in his portrait studio.
Ambrotypes can be made as negatives on transparent glass or positives on black-backed glass plates. Tintypes are often associated with Civil War-era images. The positives are made on a darkened or "Japanned" plate of lacquered metal, most often iron. Shadow details for both tintypes and ambrotypes with black backing are actually transparent, which is helpful because the image then can be underexposed slightly to cut down on lengthy exposure times. The antiquated tintype process was based on black-enamel iron plates, but now a variety of metals and backings can be used with both tintypes and ambrotypes, like colored glass, black glass, gold or mica. Pigments, dyes and tones also can be added during the development process, as well as hand tinting and many of the same effects you can use with typical film.
The tintype is also referred to as the melainotype and ferrotype, and both ambrotypes and tintypes are horizontally reversed like a mirror since you’re viewing the image from the side that has been exposed. Lettering on a sign, for example, will appear in reverse.