Improvements in or connected with the Preparation of Lithographic Stones for Half Tone and Colour Printing.
Year: 1891

page_text: Date of Application, 12th May, 1891-Accepted, 9th Apr.. 1892
COMPLETE SPECIFICATION.
Improvements in or connected with the Preparation of Lithographic
Stones for Half Tone and Colour Printing.
We BERNARD KRANTZ and HERMANN ZEISSLER, both 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 the preparation of lithographic stones for half-
tone and color printing in a shorter time and more efficiently than is possible by
any of the methods at present in use. To prepare stones for half-tone printing, we
take a photographic negative on an ordinary dry or wet plate of the picture to be
reproduced, and develope and fix the same in the usual well known manner.
From the negative, we print on to paper sensitized with the composition prepared
as follows:-Mix albumen from fresh eggs with as much dextrine as will make a
firm stiff paste, which will not stick to the hands, and which when rubbed between
the hands will crumble. This paste is then crumbled up and dried in summer in
the open air, and in cold weather in a warm room, and when dry may be preserved
in well closed vessels for some time. Then take of the dried mixture 8 oz. and
scald with hot water and pour excess of water off, then add 34 oz. by weight of hot
water to the same and put the vessel containing the same in a water bath at a
temperature of 60° to 70° Centigrade, add 6 drachms liquid ammonia and stir till
thoroughly dissolved and let it cool. Then take of the following by weight.
Yellow wax 4 parts. Mutton suet 4 parts. Marseilles soap 6 parts. Mastic in
drops 2 parts. Dragon's blood 2 parts. Dissolve and mix thoroughly over a slow
fire and allow to cool. After cooling, add to the mixture of liquid ammonia
albumen and dextrine first directed to be used-5 oz. of this latter mixture slightly
thinned with lithographic varnish and dissolve the whole with 4 oz. of potassium
bichromate, adding cold water a little at a time, till the whole becomes of the
consistency of cream. Saturate with this mixture sheets of well sized smooth
paper and dry in a dark room. The sensitized paper prepared as above described
is exposed behind the negative in a diffused light, and when printed sufficiently, the
print is laid in cold water to develope, and when developed, the print is transferred
to a stone in the following manner :-It is placed face downwards on a well smoothed
lithographic stone, and squeezed well down, so that the paper and stone are in
actual contact all over, and then the stone and paper are placed in a bath composed
as follows-Liquid ammonia 1 part by measure. Water 160 parts by measure.
We leave them in the bath for about an hour, and then peel off the paper and wash
off any excess of composition from the stone by gently rocking it in water.
next pour over the stone a solution of gall nuts consisting of 4 parts by weight of
gall nuts, boiled in 120 parts by weight of water, to fix the picture on the stone.
This solution is allowed to stand on the stone for five minutes, then washed off and
the stone dried. When dry, the picture is etched up with a solution of nitric acid
and water in the manner practised in zinc engraving; well washed with water to
remove the acid and ink rolled in. The stone is then ready for printing from, the
shadows being in relief as is usual in photo-etchings from a negative.
We
To prepare stones for colour printing, we obtain a series of photographic
negatives of different portions of the picture to be reproduced, each negative
being confined to a portion of the picture, according to the colours thereof, and the
series embodying the whole of the picture. For this purpose we suggest (though
we do not claim) in the production of the negatives, the stopping out of various
colours by the use of screens of coloured glass in the manner known to photographers
in which way negatives of portions of the picture of any particular colour or shade

page_text: of colour may easily be obtained. We find it in practice convenient to use only
screens of 5 colours, viz. red, blue, green, yellow, and grey. In this way, we get
negatives corresponding to the red, blue, green, yellow, and black and white portions
of the picture, and also to the intermediate tints which appear on two or more
negatives, e.. purple appears on both the red and blue negatives. Other methods
of obtaining negatives limited to portions of the picture may be adopted provided
that a series of negatives embodying the whole picture is obtained.
From the negatives thus prepared, we print on the sensitized paper above
described and the prints are then developed, and the portions of the picture con-
tained thereon transferred to well smoothed lithographic stones in the manner
above described for half tone printing, the print from each negative being
transferred to a separate stone. The transferred picture is then fixed on the
stones, and the stones themselves etched up in the manner above described for half
tone, the shadows being in relief. Care must be taken to register the different portions
of the picture on the various stones in the proper places they will occupy in the
completed picture.
The stones thus prepared should be printed from with transparent inks.
If the process above suggested (though not claimed) is adopted, red, blue, green,
yellow, and black inks will be used, one colour to each stone, and for producing any
intermediate tints, the stone which comprises the predominating colour must be
.more lightly etched than the stone or stones containing the less predominating
colour or colours, e.g. to produce a purple if the red predominates, the red stone
must be more lightly etched than the blue.
The shading of the picture is obtained by etching all the stones more or less
deeply as in ordinary etching processes, the shadows being in relief as in photo-
etching from a negative.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, we declare that
what we claim is :-
(I.) In the process of preparing lithographic stones for printing from, the paper
sensitized by a composition composed of the ingredients herein mentioned, in about
the proportions herein mentioned, and prepared substantially in the manner herein
described.
(II.) In the process of preparing lithographic stones for printing from, trans-
ferring the photographic print from the sensitized paper herein described to the
stone by means of a bath of liquid ammonia and water, substantially as
described.
(111.) In the process of preparing lithographic stones for printing from etching
in the manner hereinbefore described the stones to which a photographic print has
been transferred in the manner hereinbefore described, by means of nitric acid and
water in about the proportions herein mentioned.
Dated the 19th dow of Mo 1801
ERNEST SALAMAN,
61 & 62, Chancery Lane, London, Agent for the Applicants.