There is a fairly good short article on the wet plate
process at:
https://en.wikipedia.org/wiki/Collodion_process
Wet plates or Collodion was invented by Fredrick Scott
Archer about 1851 and slowly replaced the Daguerreotype. Wet
plate was itself replaced by dry plates using a gelatin emulsion
about 1880. About 1890 silver-gelatin emulsion coated on flexible
film began to supplant glass plates but never did entirely. The
great dimensional stability of glass keep them in use for a
number of purposes. Curiously enough the cellulose nitrate used
for the first flexible film support is similar to the collodion
used for the sensitive coating on wet plates. Flexible film made
motion pictures and small still cameras possible.
https://en.wikipedia.org/wiki/Photographic_film
The collodion process continued to be used in the
reprographic industry for making half tone plates for many years
after dry plates for the purpose became available. Collodion has
the advantage of extremely fine grain and can be made to have
extreme contrast which were useful properties for the process as
is the ability to strip the image layer off the glass after
processing and transfer it to the printing plate.
A good pamphlet about the half tone process is at:
https://www.getty.edu/conservation/publications_resources/pdf_publications/pdf/atlas_halftone.pdf
Eventually, self-screening films and plates were devised
which did away with the need for the difficult and dangerous wet
plate process and also with the delicate and expensive
cross-screens required.
There are many experimenting with old processes now
including collodion and much literature is available both in
print and on the web.
As a side note, one finds in fiction the idea that
photographers commonly had cyanide available in the darkroom.
This is only partly true. Potassium cyanide is a very effective
solvent for silver. It is the basis of a "reducer" (that word has
another use in photography, developers are reducers) a solution
that removes some silver. A combination of iodine and cyanide
works well for removing dark spots on negatives or prints but
ammonium thiosulfate (rapid fixer) works nearly as well as
cyanide and is not dangerous. In making half tone plates on
collodion a special reducer called Monckhoven's reducer is used
because it is both a reducer and intensifier at the same time. It
is used to sharpen up the dots on the plate but is extremely
poisonous because it contains both potassium cyanide and mercuric
chloride, two of the most toxic chemicals around. It was never
found in ordinary pictorial darkrooms but was convenient for
detective story writers.
Potassium cyanide was also used as a fixing agent for the
early collodion process but much safer substances were found.
On 2/27/2019 9:28 PM, Dave Hornford wrote:
Eric
Can you refer me to something I can read about dry, or wet, plates. I may wander into a patch of time for experimenting in the near future.
Sent from my iPhone
