Collodion process

The increased exposure time made the dry form unsuitable for the usual portraiture work of most professional photographers of the 19th century.

Invented by Dr. Richard Leach Maddox in 1871, dry gelatin emulsion was not only more convenient, but it could also be made much more sensitive, greatly reducing exposure times.

One collodion process, the tintype, was in limited use for casual portraiture by some itinerant and amusement park photographers as late as the 1930s, and the wet plate collodion process was still in use in the printing industry in the 1960s for line and tone work, mostly printed material involving black type against a white background because, in large volumes, it was much cheaper than gelatin film.

[citation needed] The wet plate collodion process has undergone a revival as a historical technique in the twenty-first century.

[3] There are several practicing ambrotypes and tintypes who regularly set up and make images, for example at Civil War re-enactments and arts festivals.

This was an improvement over the calotype process, discovered by Henry Fox Talbot, which relied on paper negatives, and the daguerreotype, which produced a one-of-a-kind positive image and could not be replicated.

As collodion is a sticky and transparent medium and can be soaked in a solution of silver nitrate while wet, it is ideal for coating stable surfaces such as glass or metal for photography.

Wet plate/collodion is also a relatively inexpensive process compared to its predecessor, and does not require polishing equipment or the extremely toxic fuming boxes needed for the daguerreotype.

[citation needed] The largest collodion glass plate negatives produced in the nineteenth century were made in Sydney, Australia, in 1875.

Well-known scientists such as Joseph Sidebotham, Richard Kennett, Major Russell, and Frederick Charles Luther Wratten attempted but never met with good results.

[citation needed] Typically, methods involved coating or mixing the collodion with a substance that prevented it from drying quickly.

Others involved more unlikely substances, such as tea, coffee, honey, beer, and seemingly unending combinations thereof.

[citation needed] Many methods worked to an extent; they allowed the plate to be exposed for hours, or even days, after coating.

They suggested that sensitive silver salts be formed in a liquid collodion, rather than being precipitated, in-situ, on the surface of a plate.

In the wet collodion process, silver nitrate reacted with a halide salt; potassium iodide, for example.

The phenotype (from Latin pannus = cloth) is a direct positive that, like the tintype, uses collodion emulsion from an underexposed image that is transferred to a dark surface so that transparent (unexposed) areas appear black and weak precipitated silver (highlights) appear brighter in reflected light, on the same principle as the daguerreotype and ambrotype.

[31] It was invented in 1852 by French photographer Jean Nicolas Truchelut, a pupil of Louis Daguerre and an itinerant daguerreotypist.

[33] Various practitioners formulated, and some patented, their own recipes with the aim of good adhesion, but a disadvantage of using such supports was that flexing of the surface caused cracking and flaking of the emulsion so few historical examples survive.

Emulsions created in this manner could be used wet, but they were often coated on the plate and preserved in similar ways to the dry process.