Improvements in or relating to Plates for Mezzotint or similar Engraving.
Year: 1894

page_text: Date of Application, 2nd Mar.. 1894
Complete Specification Left, 29th Dac., 1894-Accepted, 2nd May, 1895
PROVISIONAL SPECIFICATION.
Improvements in or relating to Plates for Mezzotint or similar
Engraving.
66
:-
I, ROBERT STEWART CLOUSTON, of Wymeswold, Watford, in the County of
Herts, Artist, do hereby declare the nature of this invention to be as follows:-
Hitherto mezzotint engravings have been engraved on copper or other plates, by
rocking" the surface of the plate or taking an electro of such surface, and on it
scraping the lights or half-tones of the picture to be engraved; thus producing a
plate with the darks on a higher level than the lights, which wears very quickly
in printing. My invention consists of a raised light plate produced by mezzotint
or other means about to be described, or any combination of them.
I take a matrix of a rocked ground, or a rocked ground treated as a matrix,
and on it I scrape the lights or half-tones, as in ordinary mezzotint; 1 then by
deposition or other means produce a reverse of this in which the lights will be high
and the darks low. The "burr" may be removed either from the original plate
from which the matrix is taken or from the plate resulting from the matrix.
Where it is requisite still further to sink the darks, I paint over such darks with
ordinary copper plate or other suitable ink or substance, and on this I dust
powdered marble dust, powdered quartz, emery powder, or any other substance
having sharp angles in its grain and preferring such substances as are not affected by
hea. The plate may then be "whirled on an ordinary whirling table to remove
such part of the dust as is not required, or it may be removed by several other
means, such as a brush, an etching point, or a scraper. For some effects I prefer
dusting the painted parts first with a very fine powder such as crocus powder or
plumbago.
The grain used may be protected from acid (if necessary) and it may be made a
conductor before dusting on, or the surface may afterwards be silvered or covered
with plumbago or any of the conductors in use.
Or the plate may be produced without a mezzotint basis, in the following manner.
1 draw on a plate of any suitable substance such as copper, zinc, xylonite &c. the
design to be produced, or I photograph the design and print it on the plate in
any of the ordinary ways. I then paint over this with a brush as before
described, and proceed similarly. I also use this method in combination with
several other forms of engraving such as photo-gravure, etching, line, stipple &c.
Where great speed in printing is requisite I protect the darks by raising small
supports to prevent the cloths used in printing from removing the ink from the
lowest of the hollowed forms.
This may be done by making minute holes in the painted parts, or, where, as in
photogravure there is a metal matrix, I drill small holes, the cast or electro of
the plate giving the required perpendicular supports.
Before painting or photographing the design or picture on the original surface,
I prefer to cover such surface-if metallic-with one of the preparations in use for
preventing adhesion to the resulting plate.
I also scrape and print from the matrices of ordinary mezzotint grounds.
1 1004

page_text: COMPLETE SPECIFICATION.
Improvements in or relating to Plates for Mezzotint or similar
Engraving.
1, ROBERT STEWART CLOUSTON, of Wymeswold, Watford, in the County of
Herts, Artist, do hereby declare the nature of this invention, and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement :-
Hitherto mezzotint engravings have been produced on copper or other plates by
"rocking "the surface of the plate or taking an electro-reproduction of such
surface, and on it scraping the lights or half-tones of the picture to be engraved;
thus producing a plate with the darks on a higher level than the lights, which
wears very quickly in printing. By my invention a raised-light plate not liable to
wear rapidly can be produced by mezzotint or other means about to be described
or by any combination of them.
•
"
For instance, I take a cast or 66 reverse of a rocked ground, or of an aqua-tint
ground, or of a grain-deposited ground, or of any similar ground, or I take any
original of these grounds and on it I scrape the lights and half tones as in ordinary
mezzotint. I then by deposition or other means produce a reverse of this in which
the lights will be high and the darks low. The "burr" may be removed either
from the original plate from which the "reverse" is taken or from the "reverse
itself or from both; or from parts of such original ground, cast, or matrix so as to
increase the difference of quality between tones or parts of the resulting plate.
"
Where it is requisite still further to sink the darks or to alter or strengthen
the ground, I paint over the whole or parts of the plate from which a cast is to be
taken with ordinary copper plate ink, which may or may not be made a conductor
of electricity, or with any other suitable ink or substance of which there are several
such as ordinary oil paint, or I mix this ink or substance with substances such as
paraffin wax which tend to liquefy with heat. Or I "ink in "with any of these or
like substances and wipe off as for proving, and on the surfaces so coated with
vehicle I dust powdered quartz, emnery powder, marble dust, powered glass, or any
other substance having regular or irregular angles in its grains, or I use a mixture of
any of them, preferring those which are not affected by heat. The plate may then
be "whirled" on an ordinary whirler to remove such part of the dust as is not
required, or such dust may be removed by any other suitable means, such as a
brush, an etching point, or scraper.
For some effects I prefer first dusting the painted parts or inked and wiped surface
with a very fine powder, such as crocus powder or plumbago, or any suitable granular
substance preferably using one having a slightly absorbent nature, so as to increase
the difference of level between the lights and darks.
The grain used may be protected from acid if necessary by any of the usual and
well known means. It will be understood that a great deal of the success of this
method depends upon the temperature of the vehicle employed at the time of dusting
on the grain for by varying the temperature the strength of the grain for printing
purposes can be varied and regulated to a very great extent.
The vehicle and the grain may be made conductors of electricity either before or
after the process of dusting, by any of the conductors at present in use, for
instance it may either be silvered or covered with plumbago or bronze powder.
The plate may be produced without the basis of a mezzotint or other ground in
the following manner :-
I draw on a plate of any suitable substance such as copper, zinc, or xylonite, the
design to be produced, or I photograph, the design and print it on the plate in
the ordinary ways, having previously, where necessary, rendered the surface non-
adhesive to the deposit. by silvering or by any of the numerous methods employed for

page_text: such a purpose.
I then paint my vehicle over this and dust it as before described.
I also use this method in combination with several other forms of engraving such
as photogravure photo-process, etching, line, stipple, either on the original plates,
or on a reverse or cast therefrom, as may be best, or by adding these or any other
form of engraving after the tints or tones have been made.
Where great speed in printing is requisite I protect the darks by raising special
small supports to prevent the cloths used in printing from removing the ink from
the lowest of the hollowed forms. This may be done by making minute holes or
lines in the painted parts prior to electrotyping or by drilling small holes or cutting
lines in the plate before or after inking in. The cast or electro will thus give the
required perpendicular supports.
I also scrape and print the caste or reverses of mezzotint and other grounds with
or without the removal of burr from the original plate, and in the latter case
where necessary I take a cast or electro of such matrix and remove the burr in
whole or part from that then making a cast or electro of the result, from which
I print.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A high-light mezzotint printing plate produced by any of the means or methods.
hereinbefore described or by any combination of them.
2. In the production of a mezzotint or other printing plate such as described the
removal of burr or roughness froin the whole or parts of the ground of the original
plate or a reverse or both.
"
is to be
3. The use in the production of a plate from which a
"reverse or copy
taken of copper plate ink or other vehicle and grain both superposed on a design or
representation etching photogravure photo-process photograph or the like on the
plate substantially as and for the purpose described.
4. A matrix of a mezzotint or other ground such as described having its darks
covered with a compound coating consisting of an outer layer of granular material
such as described and of an inner layer of copper-plate ink or other vehicle laid ou
the design.
"
5. A " reverse produced from a matrix of the kind claimed in Claim 4.
6. A matrix of the kind claimed in Claim 4 having the inner layer of its
compound coating of a substance which can be made fluid or whose fluidity can.
be increased by the application of heat substantially as and for the purpose
described.
7. The use of plumbago or crocus powder or an absorbent granular substance
and of quartz emery powder marble dust powdered glass or like heat-resisting
substances in the compound coating of the matrix substantially as and for the
purposes described.
8. The means for protecting the darks of a printing plate used in rapid printing
substantially as described.
9. Scraping on and printing from the "reverse" of ordinary mezzotint or aqua-.
tint or grain-deposited or similar grounds with or without removal of the burr
substantially as and for the purpose described.
Dated this 28th day of December 1894.
KOB, S. CLUUSTUN.
W. P. Thompson & Boult,
Agents for the Applicant..