The plate can be developed in the usual way. Try it and see the
results.--_Reported in the Beacon._
* * * * *
PLATINOTYPE PRINTING.[1]
[Footnote 1: A communication to the North London Photographic
Society.]
Platinotype, which may be considered to be the most artistic of
photographic printing processes, may be separated into its three
modifications--the hot bath and cold bath, in which a faintly visible
image is developed, and the Pizzighelli printing-out paper. The hot
bath process, again, may be divided into the black and white and sepia
papers. I intend to give you a rough outline of the preparation of the
paper and working of these modifications, concluding by demonstrating
the hot bath method, and handing around prints by it.
Platinotype may almost be styled an iron printing process, for, while
no trace of iron or its salts is found in the finished print, certain
salts of iron are mixed with the platinum salt, which is platinum
combined with two atoms of chlorine (PtCl2), as a means for readily
reducing it; this, however, cannot be effected without the presence of
neutral oxalate of potash, hence the use of the oxalate bath. There is
no platinum in the paper for the cold bath process, it being coated
with ferric oxalate mixed with a very small quantity of chloride of
mercury--somewhere about one grain to an ounce of ferric oxalate
solution.
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