AN IMPROVED METHOD OF ETCHING RELIEF PLATES FOR SURFACE PRINTING
Year: 1870

page_text: PROVISIONAL SPECIFICATION left by William Robert Lake at the
Office of the Commissioner of Patents, with his Petition, on
the 9th March 1870.-A communication from abroad by John
McLoughlin, of Morrisania, and Edmund McLoughlin, of New
York, both in the State of New York, United States of America.
I, WILLIAM ROBERT LAKE, of the "International Patent Office,"
Southampton Buildings, London, Consulting Engineer, do hereby
declare the nature of the said Invention for "AN IMPROVED METHOD OF
ETCHING RELIEF PLATES FOR SURFACE PRINTING," a communication, to be
as follows:-
This Invention consists mainly in the transforming of etched plates
into bold relief so that they can be used in ordinary printing and
embossing presses. Relief plates have heretofore been made in one of
three ways:-First, engraved by hand; second, bitten down by corrosive
acids or menstrua, the lines desired in relief having first been protected
with an oily ink or other desirable compound applied with a brush; or
third, bitten down with acids or menstrua as in instance second, and only
differing from that in having the lines desired in relief protected by a
similar compound applied by an impression from an etched plate; this
process is called transferring.

page_text: There is also an obsolete process by which the etched lines were
produced in relief by flooding the surface of the plate with some soft
metal in a melted state, which when cold was planed or ground off,
leaving the lines previously etched filled with the metal, which obviously
became raised as the surface of the original plate was bitten away.
In practising my Invention I prefer to use a zinc plate, which having
been etched and carefully cleaned is covered with a coat of varnish
and dried. The varnish found to best answer the purpose is composed
of beeswax two parts, shellac forty-eight parts, and alcohol fifty parts,
its desirable properties resting in its hardness and tenacity when dry,
and its quality to resist the action of acid. Upon being well dried the
varnish is scraped or ground from the surface of the plate, leaving the
sunken or etched lines thoroughly filled with varnish. The plate having
its reverse side and edges protected with the varnish already described
is thoroughly cleaned on the etched surface, and dipped into a metallic
solution of water and sulphate of copper until the exposed surface of
the plate is of a deep black color. It is then immersed in sulphuric
acid of the requisite biting strength, where it is allowed to remain until
the plane surface has been bitten away nearly to the depth of the
etched lines. It is then withdrawn and washed with cold water and a soft
brush. The effect of the metallic solution consists in the facility with
which by its use the bubbles of hydrogen are freed when the plate is
being acted upon by the acid. The said metallic solution may be varied
according to the kind of metal composing the plates, but should in
each case be of a solution of a metal higher in the electric scale; as,
for instance, nitrate of silver for brass or copper, chloride of gold for
silver plates, and chloride of platinum for gold plates. The metallic
solution should be weak enough not to make the black deposit in its
metallic state. The use of this solution is optional and only essential
to secure more rapid results and a somewhat higher degree of perfection
in the plate than can be attained without its use. The plate having
been carefully washed with cold water and brushed, is dried. At this
stage of the process the surface of the plate has been eaten away nearly
to the depth of the original etching, leaving a a relief composed of the
hardened varnish with which the lines in etching were originally filled.
The plate is again dipped into the metallic solution and dried then
treated with a light solution of water and gum arabic, immediately
followed by printers' ink diluted with turpentine to give it fluency,
separate sponges being used for the solution and ink. Care should be

page_text: taken to so rub the plate as to leave no portion of the raised lines
untouched, and to incorporate the ink into them until they have been
well blackened. The ink is by the gum solution kept from the body
of the plate where ink is not needed, but it unites freely with and
• covers the varnish lines where its protection is required. The gum
solution and ink having been applied the plate is then washed with
the biting acid and brush, and thoroughly dried by being subjected to
a gentle heat. When cool a finely powdered compound is sprinkled
or dusted freely over the plate. The application of a soft dry brush
then removes nearly all of the powder, except such as adheres to the
sides and surfaces of the raised lines. The powdered compound pre-
ferably used consists of common resin two pounds, good beeswax one
and one half ounce, and gum shellac one pound. The plate is then
subjected to a gentle heat, which causes the powder to freely assimilate
with the ink and varnish composing the raised lines. The edges of the
design having been protected the plate is again immersed in the
menstruum until the lines of metal stand in relief, care being taken to
not attempt to gain too much at one operation. The plate is then
washed with the metallic solution applied with a soft brush and dried.
The powdered compound is again sprinkled over the surface of the
plate followed by the use of the soft brush, care being taken this time to
move the brush in one direction only so as to secure a perfect layer of
the powder upon one side of each line to be preserved. The plate is
again heated sufficiently to unite the powder with the varnish as before,
requiring a somewhat higher degree of heat. After being cooled the
plate is again sprinkled with the powder and brushed in the opposite
direction, securing a layer of the compound upon the reverse side of the
lines acted upon before, after which the plate will again be heated for
the purpose described. The powdered compound is thus applied from
O all directions to secure the requisite protective layer on both sides of
every line in the design, after which the plate should be immersed in
the menstruum as before with the repeated protective operation already
described, until the required height of relief is obtained. That being
accomplished the plate is carefully cleansed and dried. It will then
b be observed that the summits of the raised lines were once the bottoms
of the etched lines in the original plate, and are comparatively rough
from the action of the acid during the etching process. It is then only
necessary to grind these faces upon a flat stone to adapt them to ordinary
press work or embossing. Upon close observation the lines will be

page_text: found clear and delicate, and the sides or edges of each line sharp and
well defined. It is obvious that our process differs mainly from all
others heretofore known and practised in the protection of the original
etched design as we proceed, thus preventing the destructive lateral
action of the acids or menstrua.