This process consists in converting a cliche in half tones into one in
lines, which can be directly printed on paper, or impressed, by means of
an ink transfer made as explained before, on a stone, or on a zinc or
copper plate for etching in relief, or in intaglio, according as the
cliche is negative or positive.
A cliche on gelatine, but preferably on a collodion film, is varnished
with a solution of yel
ow wax and bitumen in benzole and turpentine-oil:
Bitumen of Judaea 8 parts
Yellow wax 2 parts
Benzole 40 parts
Turpentine oil 60 parts (filter)
then etched as done to engrave in the aquafortis manner, the corrections
being made by applying with a brush some of the above varnish on the
defective parts, which are worked over when the varnish is dry.
The tools are simply needles of various thickness ground in sharp square
and round points of different sizes.
When the etching is finished, the parts which should form the ground, or
white parts of the design, being covered with the bitumen varnish is
non-actinic, or, in other words, does not admit the light acting on the
sensitive plate preparation employed to reproduce the design, except by an
exposure a good deal longer than that necessary to reduce the metallic
The engraver will see at once that, although it greatly simplifies the
copying work and, consequently, saves much time, this process does not,
however, bind him to any rules and leaves him perfectly free to follow its
inspirations and make such alterations as he thinks proper to produce
artistic effects; in a word, the reproduction will no more be a picture
taken by a mechanical process, so to say, but an original drawing
reflecting his talent and characteristic manner.
A similar process much employed by photo engravers, and presenting the
same advantages, is to convert an ordinary photograph on paper--or a blue
print, as devised by the writer--into a design in lines by drawing with
India ink, or the special ink of Higgins, and, this done, to wash off the
photographic image, the design being afterwards reproduced by the ordinary
processes as a negative or a positive cliche.
When the photograph is a silver print especially made for the purpose in
question and, consequently not toned, but simply fixed in a new
thiosulphate (hyposulphite) bath, and well washed--it is bleached by
flowing over a solution of--
Bichloride of mercury 5 parts
Alcohol 40 parts(13)
Water 100 parts
If the photograph has been toned, i.e., colored by a deposit of gold, or
if it was fixed in a thiosulphate bath in which toned prints have been
fixed, then the image is dissolved by treatment in a solution of potassium
cyanide in alcoholized water.
When a blue photograph is reduced, it is advisable before drawing upon it
to first reduce its intensity by a prolonged immersion into water. Pale
blue is a very actinic color which is not reproduced in photography,
except by the ortho-chromatic process, or if it does, the impression being
very weak, is not objectionable. When the image has not been sufficiently
or not at all bleached, the blue is dissolved by an alcoholized solution
of the blue solving.