IMPROVEMENTS IN PRODUCTION OF PRINTING AND OTHER SURFACES IN RELIEF OR INTAGLIO."
Year: 1866

page_text: LETTERS PATENT to Duncan Campbell Dallas, of 108, Fleet Street,
in the City of London, for the Invention of "IMPROVEMENTS IN
PRODUCTION OF PRINTING AND OTHER SURFACES IN RELIEF OR INTAGLIO."
PROVISIONAL SPECIFICATION left by the said Duncan Campbell Dallas
at the Office of the Commissioners of Patents, with his Petition, on the
-9th May 1866.
I, DUNCAN CAMPBELL DALLAS, of 108, Fleet Street, in the City of London,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
THE PRODUCTION OF PRINTING AND OTHER SURFACES IN RELIEF OR INTAGLIO," to be
as follows:-
⚫ Upon the surface of a glass plate, or other transparent substance capable
of transmitting the chemical rays of light, I cause to be photographed,
drawn, painted, transferred, or otherwise suitably delineated, any design or
subject in a medium which either partially or totally intercepts the said
chemical rays of light. Over the design or subject produced as aforesaid I
[Price 8d.1

page_text: pour or coat with a solution of gelatine, gluc, gum, or other analogous
material rendered sensitive to light by chromic acid, chromic salts, or other
chemical substances capable of mixing with gelatinous or similar bodies,
and rendering them insoluble after exposure to light. I next place the
coated subject or design aside to dry. When sufficiently dry I expose the
uncoated side to light, which renders the coating insoluble in warm water
wherever the light is not intercepted by the subject or design. After exposure
I pour cold water over the coated side and allow the water to remain in
contact five or ten minutes in order to soften the parts not acted upon by
the light; this also causes the image in those parts to swell up above the
parts where the light has acted; I pour off the water and cover the surface
with warm water of about 150° to 180°; this gradually dissolves the soluble
portions of the coating. Before the water has got cold I pour it off and
again cover with fresh warm water; I repeat these washings till the design
or subject appears free from the gelatinous mixture; I now put the plate
away to dry; the plate being dry I proceed in various ways according
to the object desired, thus:-
I. To obtain increased relief on the parts rendered insoluble by light I
recoat the surface with the sensitive solution, again expose to light, and
increase the degree of exposure: I then repeat the washings detailed above;
after drying I again recoat, if I consider it. necessary, expose and wash as
before. In short I add as many fresh layers of insoluble material as may be
possible or as may be deemed sufficient for building up the relief. During any
of the exposures I stop out the light where practicable by suitable means
from any parts of the subject or design where increased relief may not be
required.
II. In some instances I obtain increased relief by damping or otherwise
causing the insoluble relief to imbibe moisture; this causes the relief to
swell. By applying this method when advisable with the process described
in No. 1. the relief becomes much increased; a glue or gelatine mould does
this in many cases well.
III. If the subject or design is photographed, drawn, painted, transferred,
or otherwise delineated in a material which can be dissolved away without
injury to the insoluble relief, I employ the solvent which may be necessary,
and obliterate the subject or design, leaving the material on which it was
based bare. For example, in the case of a drawing, painting, transfer, or
photograph on glass in a black bituminous substance, as bitumen of Judea,
I dissolve the said Drawing by means of benzole or other convenient
solvent, and leave the surface of the glass bare; by this means an increase

page_text: of depth is produced, which relatively increases the original relief. I gain
also a smooth level surface at the bottom of the sunk parts, a valuable point
in many respects, among others in blocks for surface printing.
IV. If I require a granulated surface on the relief I lay all over on
aquatint ground, or I roll or dab over the surface with a sticky material
and sift powdered rosin or other granulated material over the surface.
Before or after any of the four methods above described I proceed to
take a mould or reverse of the surface. I do this either by electrotyping,
casting, or pressure.
I. In electrotyping the surface must be made conducting by the methods
most convenient; care must be taken that the electrotyping solution does not
injure the surface. This process I need not detail as it is well known to
those accustomed to electrotype glue or gelatine moulds.
II. In moulding by casting I use either well melted sulphur or the com-
position of gutta percha and oil invented by me some years ago when
carrying out the photo-galvanographic process. This composition can be
used both for casting or for pressure. I also use in some cases gelatine
or glue for taking a cast; this has the further advantage of causing the relief
to swell up.
III. To save time in electrotyping, and for other purposes, it may be
necessary to take a mould from a mould. In this case I take my first mould
in sulphur, and make from this either by casting or pressure such other
mould or moulds I may require; or I take the first mould in gutta percha
or gutta percha composition and mould upon it in plaster or any other material
which will not injure or adhere to the gutta percha.
IV. When I do not wish to electrotype the second mould, but to cast from
it in stereotype metal, I take my second mould in plaster or by the paper
method used by stereotypers.
V. The paper method of moulding used by stereotypers may also be used
to mould from the relief surface direct. The brush used in beating must not
be too hard.
VI. I also mould by thin tin, lead, or other metal foil by beating with a
brush as in the stereotype method above mentioned; or the foil may be
placed upon the relief and a softened gutta percha or other substance pressed
well upon it; the foil mould being removed can then be electrotyped.
moulds are not required the relief surface can be used for the purpose of
obtaining rubbings in the manner known to antiquaries, artists, and others.
When
The process is applicable among other things to the production of plates,
blocks, or other surfaces for embossing, printing, or otherwise working upon

page_text: typographic, copper plate, or other presses. For printing in the manner of
woodcuts I use a positive subject or design on a transparent basis, as
already described; this gives by the subsequent manipulation a more
suitable surface than the relief produced upon a negative picture.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Duncan Campbell Dallas in the Great Seal Patent Office on
the 9th November 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DUNCAN
CAMPBELL DALLAS, of 108, Fleet Street, in the City of London, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Ninth day of May, in the year of our Lord One
thousand eight hundred and sixty-six, in the twenty-ninth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Duncan Campbell Dallas, Her special license that I, the said Duncan Camp-
bell Dallas, my executors, administrators, and assigns, or such others as I, the
said Duncan Campbell Dallas, my executors, administrators, and assigns,
should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom of
Great Britain and Ireland, the Channel Islands, and Isle of Man, an
Invention for "IMPROVEMENTS IN THE PRODUCTION OF PRINTING AND OTHER
SURFACES IN RELIEF OR INTAGLIO," upon the condition (amongst others) that
I, the said Duncan Campbell Dallas, my executors or administrators, by an
instrument in writing under me, or their, or one of their hands and seals,
should particularly describe and ascertain the nature of the said Invention,
and in what manner the same was to be performed, and cause the same to
be filed in the Great Seal Patent Office within six calendar months next
and immediately after the date of the said Letters Patent.
NOW KNOW YE, that 1, the said Duncan Campbell Dallas, 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 thereof, that is to say:-
Upon the surface of a glass plate or other transparent substance capable of
transmitting the chemical rays of light I cause to be photographed, drawn,

page_text: painted, transferred, or otherwise suitably delineated any design or subject in
a medium which either partially or totally intercepts the said chemical rays
of light. I usually employ a solution of bitumen of Judea in turpentine, or
in the case of a drawing by hand, Indian ink, sepia, or other nonactinic colour.
Over the design or subject produced as aforesaid I pour or coat with a
solution of gelatine, glue, gum, or other analogous material rendered sensitive
to light by chromic acid, chromic salts, or other chemical substances capable
of mixing with gelatinous or similar bodies, and rendering them insoluble
after exposure to light. A solution consisting of gelatine 10 parts, bichromate
of potash 1 part, and water 89 parts is very suitable. I next place the coated
subject or design aside to dry. When sufficiently dry I expose the uncoated
side to light, which renders the coating insoluble in warm water wherever the
light is not intercepted by the subject or design. The time required for the
exposure will vary much with the quality of the light: in daylight it will vary
say, from one to six hours; it should be terminated as soon as the semi-
opaque portions of the design show signs of being acted on by the light, as
will be evident from a slight change on the colour of the coating. After
exposure I pour cold water over the coated side, and allow the water to
remain in contact 5 or 10 minutes, in order to soften the parts not acted
upon by the light; this also causes the image in those parts to swell up above
the parts where the light has acted. I pour off the water, and cover the
surface with warm water of about 150° to 180°; this gradually dissolves the
soluble portions of the coating. Before the water has got cool I pour it off,
and again cover with fresh warm water. I repeat these washings till the
design or subject appears free from the gelatinous mixture. I now put the
plate away to dry.
The plate being dry I proceed in various ways, according to the object
desired, thus:-
I. To obtain increased relief on the parts rendered insoluble by light I
can, if the original design has been produced in bitumen, or other medium
capable of withstanding the washing operations above described, re-coat the
surface with the sensitive solution, again expose to light, as before, but with
increased exposure. I then repeat the washings detailed above. After drying
I again re-coat, and repeat the operation, if I consider it necessary, to obtain
a further increase of relief. In short, I add as many fresh layers of insoluble
material as may be deemed suflicient for building up the relief. During any
of the exposures I stop out the light from any parts of the subject or design
where increased relief may not be required; this I do by painting in opaque
ink on the uncoated side of the plate or surface.

page_text: II. In some instances I obtain increased relief by damping or otherwise
causing the insoluble relief to imbibe moisture; this causes the relief to
swell. By applying these two methods the relief becomes much increased.
If a glue or gelatine mould be taken from the surface an increased relief will
be obtained in consequence of the surface absorbing moisture from the glue
or gelatine.
III. If the subject or design is photographed, drawn, painted, transferred,
or otherwise delineated in a material which can be dissolved away without
injury to the insoluble relief 1 employ the solvent which may be necessary,
and obliterate the subject or design, leaving the material on which it was
based bare. For example, in the case of a drawing, painting, transfer, or
photograph on glass in a black bituminous substance, as bitumen of Judea,
after the relief has been produced upon it, as above described, I dissolve the
said drawing by means of benzole, and leave the surface of the glass bare at
the parts where the gelatine coating has previously been dissolved away by
the warm water. By this means an increase of depth is produced, which
increases the relief. I gain also a smooth level surface at the bottom of the
sunk parts, a valuable point in many respects; among others, when the plate
or surface is required to produce blocks for surface printing.
IV. If 1 require a granulated surface on the relief, as in the case when I
desire to produce from it a plate to be used for printing after the manner of
copper-plate printing 1 lay all over an aquatint ground in the usual way, or
1 roll or dab over the surface with a sticky material, and sift powdered rosin
or other granulated material over the surface.
Before or after any of the four methods above described I proceed to take
a mould or reverse of the surface. I do this either by electrotyping, casting,
or pressure. •
1. In electrotyping the surface must be made conducting by the methods
most convenient. Care must be taken that the electrotyping solution does
not injure the surface; this process I need not detail, as it is well known to
those accustomed to electrotype glue or gelatine moulds.
II. In moulding by casting 1 use either well-melted sulphur or the
composition of gutta percha and oil invented by me some years ago when
carrying out the photogalvanographic process, and now well known to
electrotypers; this composition can be used also in moulding by pressure.
I also use in some cases a solution of gelatine or glue for taking a cast;
this has the further advantage of causing the relief to swell up, as already
mentioned.
III. To save time in electrotyping and for other purposes it may be

page_text: necessary to take a mould from a mould. In this case I take my first
mould in sulphur, and make from this, either by casting or pressure, such
other mould or moulds as I may require, or 1 take the first mould in
gutta percha or gutta percha composition, and mould upon it in plaster or
any other material which will not injure or adhere to the gutta percha.
IV. When I do not wish to electrotype the second mould, but to cast from
it in stereotype metal I take my second mould in plaster, or by the paper
method used by stereotypers.
V. The paper method of moulding used by stereotypers may also be
used to mould from the relief surface direct. The brush used in beating
should not be too hard, and care should be taken or the surface may be
injured.
VI. I also mould with thin tin, lead, or other metal foil by beating it with a
brush, as in the stereotype method above mentioned; or the foil may be
placed upon the relief, then covered with an adhesive material, and afterwards
softened gutta percha or other soft substance pressed well upon it.
Lastly. The foil mould being removed with its backing can then be
electrotyped. When moulds are not required the relief surface can be
used for the purpose of obtaining rubbings in the manner known to
antiquaries, artists, and others; this is a ready way to obtain an outline
to be transferred to stone or otherwise.
The process is applicable, among other things, to the production of plates,
blocks, or other surfaces for embossing or for printing. It will be seen
that in printing in the manner of woodcuts I use a positive subject or
design on a transparent basis; this gives by the subsequent manipulation, as
described, a more suitable surface than the relief produced upon a negative
picture.
Raised surfaces, prepared as above described, may be used advantageously
to produce engraved plates by machine-copying or ruling with the instrument
known as the petagraph, the irregularities of the surface which is being
copied producing undulations in the lines, whilst the instrument rules on the
copper or other plate, as is well understood.
Sunk surfaces prepared according to my Invention may also be employed
in printing so as to produce prints with half tints in imitation of those
obtained by washes of water colour or by photogenic action: this is effected
by pouring upon the plate a semi-opaque ink, then laying the paper or other
material thereon, and pressing off the excess of ink from the surface by a flat
pressure, so as to leave only the hollows filled. The paper or material being
now removed from the surface will be found to have taken the ink in different

page_text: quantities, according to the depth of the corresponding hollows. This method
of printing is now known as photo-relievo printing.
In witness whereof, I, the said Duncan Campbell Dallas, have hereunto
set my hand and scal, this Eighth day of November, in the year of our
Lord One thousand eight hundred and sixty-six.
DUNCAN C. DALLAS. (L.S.)