The plate is then washed with water, and all the
sugary coating removed, leaving the surface of the copper bare, except
where it is protected by the bitumen forming the image. The plate is
then bitten with perchloride of iron, which gives a first biting,
leaving all the lines in relief. Further depth is obtained by
alternate inkings and bitings, as in the Gillotype method.
The above processes are very interesting, the use of the sugary
coating, the hardening it by heat, and the triple exposure and biting
are new--at any rate, have not, so far as I know, been published
before.
The report then goes on to describe a further application of the same
principle to obtaining photographic images recently invented by M.
Garnier, and called by him atmography.
PHOTOGRAPHIC PRINTING BY VAPOR--ATMOGRAPHY.
This process consists in tracing or transferring by means of vapors or
fumes an image of any object from one surface to another, whence the
name of atmography it is proposed to give it. The operations are as
follows:
When an image formed of a powdery substance has been obtained either
by dusting (as described above), or by filling an engraved plate with
the powder, the plate bearing the image is exposed to a vapor, which
has no effect upon it. The powder alone absorbs the vapor, and if the
plate be then applied to a surface coated with some substance capable
of being acted upon by the vapor, an image is obtained upon this
second surface.
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