Improved Method of Photo-etching on Zinc and Copper.
Year: 1891

page_text: Date of Application, 12th May. 1891-Accepted, 9th Apr., 1892
COMPLETE SPECIFICATION.
Improved Method of Photo-etching on Zinc and Copper.
We BERNARD KRANTZ and HERMANN ZEISSLER, of 13 Bunhill Row in the
City of London, Lithographic Artists, do hereby declare the nature of the said
invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
The object of this invention is to produce by means of photo etching on zinc and
copper plates suitable for producing in "half-tone" the highest class of printed
work, such plates being prepared ready for printing from in less time and at a
smaller cost than any plates of whatever description now used for printing from.
According to our invention, we take a tin plate of suitable size and shape, and
cover the same with a coat of lamp black, and when this is dry, we coat over the
lamp black with Chinese white and thoroughly dry the plate. We then, by means
of an ordinary ruling machine, rule on the prepared plate, through the white only,
diagonal horizontal, vertical or crossed straight, waved, or jagged lines. This
operation leaves the plate showing black lines, on a white ground. We then throw
an enlarged image of the picture or design to be printed on the ruled plate by
means of a magic lantern. We then take a negative of the dimensions of the
finished print, by means of a photographic camera in the usual way, from the
picture or design as thrown on the tin plate by a magic lantern, and print from such
negative on the zine or copper plate, which has been previously sensitized with
bitumen, and develope the picture on the zinc or copper by the aid of turpentine in
the usual way.
If the plate used is of zinc, we next immerse it for about
35 minutes in a bath of three parts nitric acid, and twenty parts water by measure.
When removed from the bath we sponge off all the acidulated water with a
solution of gum arabic and water. The deep shadows will now be well visible.
We next immerse the plate for about 5 minutes in a saturated solution of carbonate
of soda and then place it under running water for a short time and lightly rub it
with a soft rag or brush for the purpose of cleaning the picture from any deposit of
nitrate of zinc. When the plate is sufficiently washed, we ink it with ordinary
printer's ink and dust it well with powdered resin, the loose powder is blown off
and the plate again immersed in the acid bath, and after allowing it to remain
therein for about an hour, we remove it therefrom and wash it well with oil of
turpentine. We next ink the plate with etching ink, composed of equal parts of
paraffin wax, tallow, and printer's ink, and replace it in the etching bath for about
35 minutes.
To accelerate the etching process, we may add to the bath for the two
last etchings, a little at a time, a small quantity of both sulphuric and hydrochloric
acids, the quantity to be in proportion to the hardness of the plate. When
sufficiently etched, the plate is mounted on wood and is then ready for printing
from. If the plate to be prepared for printing from consists of copper instead of
zinc, we for the first two etchings substitute for the nitric acid an equal quantity of
a saturated solution of per chloride of iron in the etching bath above described, the
bath for the third etching being the same as hereinbefore described for zinc plates.
Or instead of photographing an enlarged picture on to the ruled plate as herein-
before described, we may take a photographic negative direct from the picture,
drawing or object to be reproduced, and another negative (wet plate) from the ruled
plate. These negatives we place in a magic lantern, with the negative from
the ruled plate in front, and throw the combined image from both negatives for
a sufficient time direct on to the zinc or copper plate which has previously
been sensitized with bitumen. After the picture has been developed on the
plate by turpentine the plate is then etched and prepared as hereinbefore

page_text: described. This process is also suitable for preparing zinc or copper matrices
for making india rubber stamps, and for engraving zinc or copper seals or dies
in intaglio or relief, but when engraving in relief is required, a positive
photograph must be used instead of a negative.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, we hereby declare that
what we claim is :-
(I.) In the process of photo etching on zinc and copper, the taking of a
photograph from a picture or design thrown by a magic lantern on to a ruled plate,
as and for the purpose herein before stated.
(II.) In the process of photo etching on zinc and copper the throwing. by a
magic lantern of the combined image from two negatives on
a zinc or copper
plate sensitized with bitumen substantially as described.
(II.) The improved process of photo-etching on zinc and copper, substantially
as herein described.
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ليقد
J
CM1001
ERNEST SALAMAN,
61 and 62, Chancery Lane, London, Agent for the Applicants.