The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1869-01-25
Mechanical Photographic Printing.

Photographic printing by mechanical agency
is the latest novelty in England. The London
papers describe the invention, which was pup
lcy exhibited last month. the Star says:-
"Unlike the present me' hod ofproducing a Pho
tographic impression from negative, IN Whlch
the darkening power of salts OF silver, &C.,
under the action of light, is the medium used,
impressions so resembling those obtained as to
be iBdstnguishable from them are by the
Woodbury. process obtained by purely mechani-
cal means in printing press. The fact OF
being able to produce impressions resembling
photographs in their beautiful gradatlons OF
lone, without any necessity tor light, and the
great multiplying power gwen oy the process,
produced in remarkably short space OF time.
The operation is as iollows:-
"a thin film of gelatine, containing bichro-
mate of ammonia, is placed under an ordinary
negative, and exposed to light. The effect upon
the gelatine is to render It insoluble wherever
acted on by the light. The whole is placed in
warm water, and the parts OF the film where the
light has not acted, in consequence OF the par
tial opacity Of the negative, are soon dissolved
away, leaving mould of various thicknesses.
This when dry is placed between two steel
plates in contact with sheet Of lead hardened
with antimony, and subjected to a hydraulic
pressure of from forty to two hundred TONS
according to the size OF the plate, which causes
the geaine relief 10 impress all It's details into
the metal and, strange as 1t may seem, the
operation may be repeated with the identical
gelatine for, say, forty or fifty times, withou t
Its sustaining the slightest injury, and each i'm
perfect as the first. The metal plate is then
ready tor the press, whence pictures can be
struck off purely mechanically.
''Were this intagiO plate used in the same
manner as a wooden block, and covered with
the ordinary printing ink, the result would be
certain masses OF black and white, but no hall
tones whatever. Therefore, to obtain print
from this plate that shall have all the gradations
from black to white, as appear in photograph,
1T is necessary to revert to another mode OF
taking the impression. This is done by casting
from the metal mouid-a small quantity of color
mixed with water and gelatme is poured upon
it, sheet OF paper placed thereon. A perfectly
true surface being npw brought to bear, all
superfiuous ink is squeezed out at the edge, and
when the gelatine contained in the ink has had
time to set the paper is lifted off, taking with it
the cast or print of the mould. The plints sub
sequently are passed through hXlng BATH,
which renders the material perfectly insoluble
by process analogous to tanning.
Among the advantages said to be possessed
by this process over all others are-the pictures
can be produced In any shade OF any color, aud
every copy of the same mould shall correspond
In tone; they are perfectly permanent, and, in
addition, can be produced in any quantity with
great speed and economy. The process is cer-
tainly very interesting, and calculated to pro-
duce quite revolution in the copying of photo
graphs. The whole system Is 10 be seen any
day In operation at the works at Brompton."