The albumen print was invented by Louis-Désiré Blanquart-Evrard (1802-72) in 1850, and it was the most prevalent type of print until the 1890s. A photograph can be identified as an albumen print from the slight sheen (due to the use of egg-white) on the top surface. Almost all of the photographs produced in late 19th century Singapore were albumen photographs.
An albumen print was made by floating a sheet of thin paper on a bath of egg white containing salt, which had been whisked, allowed to subside, and filtered. This produced a smooth surface, the pores of the paper having been filled with albumen. After drying, the albumenised paper was sensitised by floating it on a bath of silver nitrate solution or by brushing on the same solution. The paper was again dried, but this time in the dark. This doubly coated paper was put into a wooden, hinged-back frame, in contact with a negative, usually made of glass but occasionally of waxed paper.
After printing, which sometimes only required a few minutes but could take an hour or more, the resultant proof, still unstable, was fixed by immersing it in a solution of hyposulfite of soda ('hypo') and water and then thoroughly washed to prevent further chemical reactions. The print was then dried. Gordon Baldwin, 'Looking at Photographs', J. Paul Getty Museum, 1991
WET-PLATE COLLODION PROCESS
The wet collodion process was invented in 1848 by F. Scott Archer (1913-57) and published by him in 1851. It was prevalent from 1855 to about 1881. Wet-collodion-on-glass negatives were valued because the transparency of the glass produced a high resolution of detail in both the highlights and shadows of the resultant prints and because exposure times were short, ranging from a few seconds to a few minutes, depending on the amount of light available.
Collodion is guncotton (nitrocellulose) dissolved in ethyl alcohol and ethyl ether. In the wet-collodion process, collodion was poured from a beaker onto a glass plate tilted to quickly produce an even coating. When the collodion had set but not dried, the plate was made light sensitive by bathing it in a solution of silver nitrate, which combined with the potassium iodide in the collodion to produce light-sensitive silver iodide. The plate in its holder was then placed in the camera for exposure while still wet - hence the name of the process. After exposure the plate was immediately developed in a solution. Gordon Baldwin, 'Looking at Photographs', J. Paul Getty Museum, 1991
DRY-PLATE GELATINE PROCESS
The wet-plate was not without disadvantage. The plates needed to be processed while still wet which meant a portable dark-room for landscape photographers. In 1871, Richard Leah Maddox introduced using gelatine for coating dry plates which could be processed later. This became a popular process for amateur photographers who could take their photographs using dry-plates and get them processed at a studio. In Singapore, its use probably started in the late 1880s (the amatuer Straits Photographic Society was established in 1889 at Hill Street) and became common from the 1890s onwards.