CERTAIN IMPROVEMENTS IN ENGRAVING
Year: 1874

page_text: LETTERS PATENT to Paul Emile Placet, of Paris, in the Republic
of France, Engineer, for the Invention of "CERTAIN IMPROVEMENTS
IN ENGRAVING."
Sealed the 3rd November 1874, and dated the 21st May 1874.
PROVISIONAL SPECIFICATION left by the said Paul Emile Placet at
the Office of the Commissioners of Patents, with his Petition, on
the 21st May 1874.
I, PAUL EMILE PLACET, of Paris, in the Republic of France,
Engineer, do hereby declare the nature of the said Invention for "CERTAIN
IMPROVEMENTS IN ENGRAVING," to be as follows:-
The processes as a whole which I am about to describe enable me by
the aid of certain chemical reactions to obtain engravings possessing
naturally the grain which is indispensable when it is wished to use the
ordinary means of impression,

page_text: The following are the principles on which depends the production of
these grained engravings:-
An animal or vegetable substance is dipped first into a liquid which
has the property of dissolving it, and then into a second liquid having a
tanning or contracting property; the whole surface of that substance is t
soon covered by a grain caused by the contractions which the substance
undergoes. The thickness, form, and depth of this grain vary according
to the substances and the liquids employed, according to the duration
of immersion, the temperature, and the degree of concentration of the
liquids.
1st. For example, a sheet of gelatine being dipped first into a
saturated solution of bi-chromate of potash, and then into a second solu-
tion thus composed :-Sulphate of iron 40; acetic acid 10%; water 100%;
in a few moments the surface of the sheet of gelatine is found to be
covered with a magnificent and very uniform grain.
In certain cases the dissolving and tanning substances may be applied
in the form of solids reduced to powder.
2ndly. If on this sheet of gelatine a drawing has been previously
printed or traced in varnish or fatty matter, and the sheet of gelatine be
plunged into the two above mentioned liquids, in this case a surface is
obtained which is grained everywhere with the exception of those parts.
occupied by the drawing, and the pressing of that surface or its repro-
duction by electro-typy gives a surface fit for printing, or any other use.
3rdly. If instead of forming the design by hand a light be used to
form it, a sun-engraving is obtained. For this it is sufficient to sensitize
the sheet of gelatine and to expose it to light under a negative or
"cliché" in the ordinary manner before plunging it into the liquids
above mentioned. In this case the light renders each point of the
gelatine layer more or less permeable to the liquids, according to the
corresponding intensity of the negative.
It follows that the liquids penetrating more or less deeply into the
gelatine, produce in each point a grain of a size and depth proportional
to the corresponding intensity of the negative or "cliché," so that by
this means a sun engraving is obtained which is a faithful reproduction
of the photograph with all its details and its smallest gradations of
tints.

page_text: Such is the nature of the processes of engraving which I desire to
have secured to me by Letters Patent, whatever may be the substances
employed, the mode of operation, and the various applications.
The following are examples of several modes of operating:-
1st. I take a leaf of gelatine paper and sensitize it with bi-chromate
in the ordinary manner. After having exposed this leaf to light under
a negative or "cliché," I dip it into the saturated solution of bi-chromate
of potash; then rapidly removing the excess of liquid with a cloth or
blotting paper I plunge it into the solution of sulphate of iron men-
tioned above; instantly the design is developed and grained. A few
seconds suffice if the exposure to light has been suitable. It is dried
and the engraving is finished. Nothing remains but to press it by some
means to have at once a plate which may serve either for impression or
for any other use.
2ndly. I take a paper covered with a layer of gelatine, sensitize it,
and expose it to light under a negative (cliché) in the ordinary way.
Then I place the paper on another surface, either flexible or rigid, so as
to be able to develope the image on the reverse side. The reversed
proof is then developed in a solution of bi-chromate of potash which
dissolves out all the parts of the gelatine which the light has not modified,
and when the image has sufficiently come out it is plunged into the
solution of sulphate of iron where it is covered with grain ready for
moulding.
3rdly. A proof in gelatine called "carbon," obtained by ordinary
means may even be grained ("graisser "). To accomplish this it suffices
to let the proof remain some time in a solution of ammonia, then in a
solution of potash, of hypochlorite of lime or any other solution having
the property of re-dissolving the gelatine rendered insoluble by light.
The proof is then plunged into the solutions of bi-chromate of potash and
of sulphate of iron where the grain quickly appears, especially if the
solutions have been warmed.
4thly. In certain cases it is advantageous to operate on plane and
rigid surfaces. Then the gelatine is run over plates of glass, metal, or
of any other substance. The gelatine may be sensitized at the moment
of running over the plates, or only after being dried. The operation
afterwards is like that described for gelatinized paper,

page_text: 5thly. The tanning material may also be applied in the solid state.
In this case after having plunged the layer of gelatine into the first
dissolving solution, the image is developed by placing its surface in
contact with a tanning powder or one having a strong affinity for water;
such as gallic acid, tannic acid, alums, sulphate of iron, lime, cements,
several chlorides, and other substances capable of producing a chemical
reaction in presence of the bodies already existing in the layer of
gelatine. Substances acting as solvents may equally be used in the solid
state by employing them in the form of powders on the gelatine slightly
wetted.
In the preceding descriptions gelatine has only been indicated by way
of example in order to facilitate the explanation of the different
methods. With more or less advantage instead of gelatine, gums,
albumen, dextrine, isinglass, sugar, caramel, glucose, casein, starch,
("amidon,") gluten, juices, or various extracts, bitumen, soaps, resins,
or other analogous substances. It is often preferable to employ a
mixture of two or several of these substances. The difference of solu-
bility of the mixed substances favours the formation of the grain; all
these substances moreover may be considered, even in the pure state, as
being a mixture in variable proportions of a soluble body, and of a body
less soluble. Thus gelatine is always composed of a certain part soluble
in cold water, and of another part insoluble.
The gelatines found in commerce are always variable in their compo-
sition, consequently the nature of the grain they produce, by the methods
above described, often varies from one operation to another.
In order to obtain results always constant and regular it is preferable
not to use pure gelatine, but to mix it with a certain proportion
of gum, albumen, dextrin, &c. &c., or better, with soluble gelatine which
gives a more homogeneous mixture. This soluble gelatine is obtained
by treating ordinary gelatine with an acid or by prolonged boiling.
The following is a mixture and a manner of working which answers
very well for the reproduction in sun engravings of the most delicate
photographs. It is only an example; it is evident equally sucessful
results might be obtained in other ways :-
-
6. On a plane surface the following mixture is poured :-Gelatine, 10;
ashlealation 7 to 2. water 100.
1 to 3. hi-chromato 1 to 2

page_text: Sometimes a small quantity of acid is added, such as chromic acid,
acetic acid, citric or other acid. It is allowed to dry, and exposed to
light under a negative or positive photograph, according to the kind of
engraving intended to be produced. The proof is then dipped into pure
water or into water rendered denser by means of borax or other matter.
The image will be instantly developed and grained.
To stay the action of the liquid the proof is plunged rapidly into the
following bath-Water, 100; alcohol, 20 to 30; ammonia, 2 to 4. It
is wiped immediately with blotting paper and left in darkness until
completely or nearly dry; then it is dipped into the solution of
sulphate of iron already mentioned. The grain forms afresh and when
the proof is perfectly developed it is plunged into pure water or into
water slightly acidulated. To stay the developement it is dried, and the
grained image is then definitely fixed and finished.
During the developement the size and depth of the grain can be.
varied according to the subject treated. For this purpose two or even
three solutions are prepared beforehand containing different quantities
of sulphate of iron and of acid. The developement is commenced by the
solution which has the least action, and is continued with one or other
of the solutions, according to the result desired to be obtained.
It will be seen by what precedes that the substances used as solvents
necessarily vary with the substances used. They are water, acids, salts
of all natures, alcohol, ether, oils, essences, &c., and mixtures of these
bodies.
The tanning matters vary also according to the substances employed;
they are gallic acid, tannic acid, salts of alum, chrome, zinc, iron,
especially the sulphate and nitrate of iron, all astringents, all bodies.
having affinity for water even in the solid state, lime in powder and
cements, the chlorides of sodium, calcium, mercury, platinum, lastly,
alcohol, ether, essences et cætera, et cætera. Thus for example, alcohol
forms a very fine grain on a mixture of gum-lac in solution in ammonia
or borax.
In order to render the action of the disolving and tanning or astringent
liquids more prompt and regular, it is often well to add to them a little
acid or a chloride, sulphate, nitrate, or other salt. Heat also greatly
assists the action of these liquids.

page_text: The methods of obtaining images naturally grained may be multiplied
and varied to infinity; for a very large number of substances produce
surfaces rough, striated, crackled, or grained by their contact with
divers appropriate chemical products. I do not limit myself to the
methods above described by way of example, my Invention consisting
in the producing of naturally grained engravings by the successive use
of two actions, one dissolving and the other tanning or contracting as
above set forth, and I reserve the right of varying the substances, the
mixtures, and the mode of operating.
I also reserve the right of applying this kind of engraving to every
branch of the arts, sciences, and industry.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Paul Emile Placet in the Great Seal Patent
Office on the 19th November 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, PAUL
EMILE PLACET, of Paris, in the Republic of France, Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-first day of May, in the year
of our Lord One thousand eight hundred and seventy-four, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Paul Emile Placet, Her special license,
that I, the said Paul Emile Placet, my executors, administrators, and
assigns, or such others as I, the said Paul Emile Placet, 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 "CERTAIN IMPROVE-
MENTS IN ENGRAVING," upon the condition (amongst others) that I, the said
Paul Emile Placet, my executors or administrators, by an instrument in
writing under my, or their, or one of their hands and scals, should parti.
cularly 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

page_text: 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 I, the said Paul Emile Placet, 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) :—
The processes as a whole, which I am about to describe, enable me by
the aid of certain chemical reactions to obtain engravings possessing
naturally the grain which is indispensable when it is wished to use the
ordinary means of impression.
The following are the principles on which depends the production of
these grained engravings:-
An animal or vegetable substance is dipped first into a liquid which
has the property of dissolving it, and then into a second liquid having a
tanning or contracting property; the whole surface of that substance is
soon covered by a grain caused by the contractions which the substance
undergoes. The thickness, form, and depth of this grain vary according
to the substances and the liquids employed, according to the duration of
immersion, the temperature, and the degree of concentration of the
liquids.
1st. For example, a sheet of gelatine being dipped first into a saturated
solution of bi-chromate of potash, and then into a second solution thus
composed-Sulphate of iron 40, acetic acid 10, water 100. In a few
moments the surface of the sheet of gelatine is found to be covered with
a magnificent and very uniform grain.
In certain cases the dissolving and tanning substances may be applied
in the form of solids reduced to powder.
2ndly. If on this sheet of gelatine a drawing has been previously
printed or traced in varnish or fatty matter, and the sheet of gelatine be
plunged into the two above-mentioned liquids, in this case a surface is
obtained which is grained everywhere with the exception of those parts
occupied by the drawing, and the pressing of that surface, or its repro-
duction by electrotypy, gives a surface fit for printing or any other
use.
3rdly. If instead of forming the design by hand a light be used to
form it, a sun engraving is obtained. For this it is sufficient to sensitize

page_text: the sheet of gelatine, and to expose it to light under a negative or cliché
in the ordinary manner before plunging it into the liquids above
mentioned. In this case the light renders each point of the gelatine
layer more or less permeable to the liquids, according to the corros-
ponding intensity of the negative.
It follows that the liquids penetrating more or less deeply into the
gelatine produce in each point a grain of a size and depth proportional
to the corresponding intensity of the negative or cliché, so that by
this means a sun engraving is obtained, which is a faithful reproduction
of the photograph with all its details and its smallest gradations of
tints.
Such is the nature of the processes of engraving which I claim to have
secured to me by the hercin-before in part recited Letters Patent, what-
ever may be the substances employed, the mode of operation, and the
various applications.
The following are examples of several modes of operating:-
1st. I take a leaf of gelatine paper and sensitize it with a bi-chromato
in the ordinary manner. After having exposed this leaf to light under
a negative or cliché, I dip it into the saturated solution of bi-chromato
of potash, then rapidly removing the excess of liquid with a cloth or
blotting paper I plunge it into the solution of sulphate of iron mentioned
above; instantly the design is developed and grained. A few seconds
suffice if the exposure to light has been suitable. It is dried, and the
engraving is finished. Nothing remains but to press it by some means
to have at once a plate, which may serve either for impression or for any.
other use.
2ndly. I take a paper covered with a layer of gelatine, sensitize it,
and expose it to light under a negative or "cliché" in the ordinary way.
Then I place the paper on another surface, either flexible or rigid, so as
to be able to develope the image on the reverse side. The reversed
proof is then developed in a solution of bi-chromate of potash, which
dissolves out all the parts of the gelatine which the light has not
modified, and when the image has sufficiently come out it is plunged
into the solution of sulphate of iron, where it is covered with grain
ready for moulding.
3rdly. A proof ("une épreuve ") in gelatine, called "carbon," obtained
by ordinary means may even be grained ("grainer"). To accomplish this

page_text: it suffices to let the proof remain some time in a solution of ammonia, then
in a solution of potash, of hypochlorite of lime, or any other solution
having the property of redissolving the gelatine rendered insoluble by
light. The proof is then plunged into the solutions of bi-chromate of
potash and of sulphate of iron, where the grain quickly appears, especially
if the solutions have been warmed.
4thly. In certain cases it is advantageous to operate on plane and
rigid surfaces. Then the gelatine is run over plates of glass, metal, or
of any other substance. The gelatine may be sensitized at the moment
of running over the plates or only after being dried. The operation after-
wards is like that described for gelatinized paper.
5thly. The tanning material may also be applied in the solid state.
In this case, after having plunged the layer of gelatine into the first
dissolving solution, the image is developed by placing its surface in
contact with a tanning powder, or one having a strong affinity for water,
such as gallic acid, tannic acid, alums, sulphate of iron, lime, cements,
several chlorides, and other substances capable of producing a chemical
reaction in presence of the bodies already existing in the layer of
gelatine. The metallic powders are in this category. Substances acting
as solvents may equally be used in the solid state by employing them in
the form of powders on the gelatine slightly wetted.
In the preceding descriptions gelatine has only been indicated by way
of example, in order to facilitate the explanation of the different
methods. With more or less advantage instead of gelatine gums,
albumen, dextrine, isinglass, sugar, caramel, glucose, casein, starch,
gluten, juices or various extracts, bitumen, soaps, resins, or other
analogous substances can be used. It is often preferable to employ a
mixture of two or several of these substances. The difference of solu-
bility of the mixed substances favours the formation of the grain. All
these substances moreover may be considered even in the pure stato as
being a mixture in variable proportions of a soluble body, and of a body
less soluble. Thus gelatine is always composed of a certain part soluble
in cold water, and of another part insoluble.
The gelatines found in commerce are always variable in their com-
position, consequently the nature of the grain they produce by the
methods above described often varies from one operation to another.

page_text: In order to obtain results always constant and regular it is preferable
not to use pure gelatine, but to mix it with a certain proportion of gum,
albumen, dextrin, &c., &c., or better with soluble gelatine, which gives
a more homogeneous mixture. This soluble gelatine is obtained by
treating ordinary gelatine with an acid, or by prolonged boiling.
The following is a mixture, and a manner of working, which answers
very well for the reproduction in sun engravings of the most delicato
photographs. It is only an example; it is evident equally successful
results might be obtained in other ways.
6. On a plane surface the following mixture is poured :-Gelatine, 10;
soluble gelatine, 1 to 2 ; water, 100; sugar, 1 to 3; bi-chromate, 1 to 2.
Sometimes a small quantity of acid is added, such as chromic acid, acetic
acid, citric or other acid. It is allowed to dry, and exposed to light
under a negative or positive photograph, according to the kind of
engraving intended to be produced; the proof is then dipped into pure
water, or into water rendered denser by means of borax or other matter.
The image will be instantly developed, and grained.
To stay the action of the liquid the proof is plunged rapidly into the
following bath:-Water, 100; alcohol, 20 to 30; ammonia, 2 to 4. It is
wiped immediately with blotting paper, and left in darkness until com-
pletely or nearly dry. Then it is dipped into the solution of sulphate of
iron already mentioned. The grain forms afresh, and when the proof
is perfectly developed it is plunged into pure water or into water slightly
acidulated. To stay the developement it is dried, and the grained image
is then definitely fixed and finished.'
During the developement the size and depth of the grain can be
varied, according to the subject treated. For this purpose two or even
three solutions are prepared beforehand containing different quantities
of sulphate of iron and of acid. The developement is commenced by the
solution which has the least action, and is continued with one or other
of the solutions, according to the result desired to be obtained.
It will be seen by what precedes that the substances used as solvents
necessarily vary with the substances used. They are water, acids, salts
of all natures, alcohol, ether, oils, essences, &c., and mixtures of these
bodies.
The tanning matters vary also according to the substances employed.
They are gallic acid, tannic acid, salts of alum, chrome, zinc, iron,

page_text: especially the sulphate and nitrate of iron, all astringents, all bodies
having affinity for water, even in the solid state, lime in powder and
cements, the chlorides of sodium, calcium, mercury, platinum, lastly
alcohol, ether, essences, et cætera, et cætera. Thus, for example, alcohol
forms a very fine grain on a mixture of gum-lac in solution in ammonia
or borax.
In order to render the action of the dissolving and tanning or
astringent liquids more prompt and regular it is often well to add to
them a little acid or a chloride, sulphate, nitrate, or other salt. Heat
also greatly assists the action of these liquids.
1
To render the substances sensitive to light the salts of gold, silver,
chrome, iron, platinum, uranium, mercury, and other metals, and also
certain substances of animal or vegetable origin may be used.
The grained images or designs obtained by means of the processes
just above explained may in certain cases be used just as they are 1
obtained either as photographic proofs, or to serve directly for impres-
sions in copper engraving, lithographic or typographic engravings.
A certain number of proofs in oily inks can always be taken from
them and transferred to stone or zinc to make lithographs or typographic
plates or blocks. The images developed as mentioned above by means 2
of suitable substances may be applied on a metal or other kind of plate,
and a perfect engraving produced there by the effect of the chemical
reaction which takes place between the plate acting as a support and
the substances contained in the image. But mostly these grained
designs to be usefully applied to the purposes for which they are 2
intended should be reproduced in a more solid and durable matter.
Reproduced by electrotypy they serve for all kinds of typographic
impressions, or in copper, on paper, leather, stuffs, wood, porcelain, &c.
The grain which these plates naturally possess enables me, by means of
copper engraving, to obtain transferred proofs on stone for lithography, 3
and especially transferred proofs on zinc, which are then transformed
into typographic plates by known means. The engraved plates
obtained by these processes may receive into their cavities incrustations
of precious metals, niello engravings or enamel after the manner of
$6 emaux cloisonnès."
In certain cases these plates present on their surfaces true bas-reliefs,
mi
8

page_text: designs, gilt or silvered, can be used for ornamenting the woodwork of
apartments, the furniture, cabinets, mantelpieces, &c.
These plates,
with designs of extreme fineness reproduced in gold, platinum, or silver,
may be applied in jewellery or goldsmiths' work.
Lastly. These same plates reproduced in resisting metals may be used
to figure, emboss, or mould metals, wood, paper, stuffs, leather, glass,
porcelain, &c. Moreover the ease and cheapness with which such
engravings can be obtained will necessarily lead to new applications
which have not been thought of at present because of the high price of
engravings done by hand.
The methods of obtaining images naturally grained may be multiplied
and varied to infinity, for a very large number of substances produce
surfaces rough, striated, crackled, crystallized, or grained by their
contact with divers appropriate chemical products.
I do not, therefore, limit myself to the methods above described by
way of example, my Invention consisting essentially in the producing of
naturally grained engravings by the successive use of two actions, one
dissolving and the other tanning, contracting, or crystallizing as above.
set forth, and I reserve the right of varying the substances, the mixtures,
and the mode of operating.
I also reserve the right of applying this kind of engraving to every
branch of the arts, sciences, and industry.
In witness whereof, I, the said Paul Emile Placet, have here.
unto set my hand and seal, this Fourteenth day of November,
in the year of our Lord One thousand eight hundred and seventy-
four.
PAUL EMILE PLACET. (L.S.)