IMPROVED PHOTOCHEMICAL PROCESS AND APPARATUS FOR THE PRODUCTION OF METALLIC PLATES FOR PRINTING PURPOSES IN GENERAL, FOR JEWELLERY, SIGNBOARDS, AND PLATES."
Year: 1878

page_text: LETTERS PATENT to Alfred Michaud, Chemist, of No. 1, Rue Laffitte, Paris,
for the Invention of "IMPROVED PHOTOCHEMICAL PROCESS AND APPARATUS
FOR THE PRODUCTION OF METALLIC PLATES FOR PRINTING PURPOSES IN
GENERAL, FOR JEWELLERY, SIGNBOARDS, AND PLATES."
PROVISIONAL SPECIFICATION left by the said Alfred Michaud at the Offico
of the Commissioners of Patents on the 17th May 1878.
ALFRED MICHAUD, Chemist, of No. 1, Rue Laffitto, Paris. "IMPROVED PHOTO-
CHEMICAL PROCESS AND APPARATUS FOR THE PRODUCTION OF METALLIC PLATES
FOR PRINTING PURPOSES IN GENERAL, FOR JEWELLERY, SIGNBOARDS, AND PLATES."
My improved process consists in applying a gelatinous bichromate negative, pro-
duced in the ordinary well-known mauner and developed on a metallic plate, on a
metallic alloy contained in a vase, and which has been readily fused by heat, such as
a mixture of fusible metal, 1000 parts (or the kind known in France as d'arceţ
metal), and 110 parts of mercury (but the proportions of which two ingredients may
vary according to the desired hardness of the cast), with a slight pressure, whereby
I obtain, after cooling, a hollow negative (if the primitive negative is a photographic
negative) which can then be used.
Firstly. To obtain direct proofs either for transferring on stone according to the
ordinary processes, or on metal if for typographic printing.
Secondly. To produce a galvano raised mould susceptible of reproducing also
galvanically an indefinite number of hollow or sunk proofs in unlimited numbers, of
any size, for jewellery or copper-plate printing.
The proofs obtained by the exposure to light of the bichromated gelatine are of
two descriptions; if the photographic negative employed is simply a reproduction
of lines, it can be employed as it is, either reversed or not; if on the contrary, it is
Drina 71

page_text: a photographic negative from nature or from an artistic drawing of any kind,
either reversed or not, this negative is first covered with a pellicle of almost
imperceptible thickness, which gives the necessary grain of the impression, which is
transmitted by exposure to light to the gelatinous proof and' consequently to the
metallic plate destined for the printer.
In order to obtain the grain for the impression a sheet coated with coloured gela-
tine and bichromated is exposed to light under a glass plate uniformly coated with
an opaque powder; this sheet is then applied under water on the negative, var-
nished with gum containing just a trace of chromic salt, then developed in tepid
water, which carries off the gelative not solarized, without touching the insoluble
parts which form the grain in question.
In order to obtain engraved galvanic plates regular with copper, which is good and
economical, I make use of a modified ordinary simple pile as follows:-The copper
solution is contained in a rectangular wooden vase, varnished externally and
coated internally with a resisting mixture composed of wax, rosin, red ochre, and
tale; my new porous rectangular diaphragms which furnish the electrical current are
immersed in this solution.
These diaphragms are composed of two simple plales with a projecting outer rib
in porous ware, semi-baked, the thickness and dimensions of which may vary
according to requirements; these two plates are set in a gutta percha fraining or in
a wooden one protected by a rosisting varnish, or in these two materials combined,
or in any other appropriate material so as to form a rectangular or square and deep
box, the two porous vertical sides being opposing, and these united by the bottom and
two other sides by the gutta percha framing or wood protected by the resisting varnish
mentioned. It is within this diaphragm that the zinc plates are immersed, being
suspended from a longitudinal rod in acidulated water, the galvanic action being
produced and acting in the usual manner.
The advantages of these rectangular porous elements are evident, they are as
follows:-
Firstly. They can replace nearly all the diaphragms known up to the present day,
in piles for one or for two liquids.
Secondly. Their dimensions may be, so to speak, unlimited, since their manufacture
is easy and certain of success.
Thirdly. Consequently the quantity of electricity can be easily obtained as required,
for not only the zinc plate can be more or less large but utilized as well on both
of its faces.
Fourthly. These diaphragms can be used with all kinds of liquids and are not to
be compared with cloth or organic membranes of any kind, which have been
proposed but are not practicable.
Fifthly. Their rectangular form has the advantage in a single pile to furnish a
deposit which operates parallelly and uniformly.
Sixthly. These diaphragms are oconomical to make and easy to keep in repair.
Seventhly. Lastly, by means of a glass syphon, either fixed or moveable, the
exciting liquid they contain can be renewed continuously, and a long, constant, and
regular duration assured.
As regards signboards and plates intended to replace the ordinary engraved plates
they may also be obtained by using bitumen in solution instead of gelatine, and then
the negative is used in its ordinary way; after a sufficient exposure in the sun it
is submitted to essence of turpentine, and then washed in an abundance of water;
it is immersed in a galvanic bath, which may vary as required, by means of the
dissolved metal; the solarized bitumen is cleaned off, and finally the plate is immersed
for an instant in a solution of ammoniacal carbonate of copper; or if it is desired to
sink somewhat the design on the plates they are allowed to remain a few minutes
in a slightly acid solution of salts of copper before producing the re-action of the
ammoniacal salt above mentioned.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alfred Michaud in the Great Seal Patent Office on the 16th
November 1878.
ALFRED MICHAUD, Chemist, of No. 1, Rue Laffitte, Paris. " IMPROVED
PHOTOCHEMICAL PROCESS AND APPARATUS FOR THE PRODUCTION OF METALLIC
PLATES FOR PRINTING PURPOSES IN GENERAL, FOR JEWELLERY, SIGNBOARDS, AND
PLATES."
My Invention has reference to the well-known photographic process in which the
action of light on bichromated gelatine or on bitumen is made use of for reproducing
casts or moulds, sunk or in relief, from photographic negatives, or positives, as the cnso
may be, and it consists,―
Firstly. In improvements in the treatment of such gelatinous bichromated plates.
And, Secondly. In improvements for obtaining therefrom metallic casts or moulds
available for different purposes, as hereafter stated.
According to the first part of my Invention, when proofs are required from a
bichromated plate taken from a negative after nature or a work of art, in order to
produce a grain on the said proofs printed therefrom, I dust uniformly on a glass
plate an opaque powder, and then cover the same with a carbon sheet conted with
colored bichromated gelatine, and expose it to the light, after which exposure it is
applied under water to the negative, previously coated with gum containing a trace
of chromic salt, and then developed in tepid water, which carries off the gelatine
that has not been acted on by light, leaving the insoluble parts thereof, forming
the required grain, adhering to the negative in the shape of an exceedingly fine
pellicle.
When a metallic cast is to be taken from a bichromated gelatinous negative,
after the same has been developed in the usual manner, I dry it in the open air,
and then place it in a closed case, at the bottom of which I place blotting paper or
other similar absorbing substance damped with water, the glass plate being separated
from the blotting paper by a few glass rods; after remaining from one to several
hours in this box it is extracted therefrom; the gelatine thereby slightly swollen is
slightly coated with very fine plumbago by means of a very fine brush, and in this
state the plate is ready to be cast from.
According to the second part of my Invention I produce a metallic mould or cast
from a gelatinous bichromated negative or positive mounted on a metal plate, as the
case may be, by the use of alloy of metals fusing at a relatively low temperature,
and by means of a slight pressure; for this purpose I make use of 1100 parts by
weight of an alloy known in France as d'Arcet metal, containing bismuth 1, tin 0.50,
and lead 0.50, to which I add 100 parts by weight of mercury; I place this alloy
in an open case wherein it is fused in any appropriate manner, or I pour it previ-
ously fused, in this case, then lay the bichromated proof thereon face downwards,
applying the same with a slight pressure such as is readily obtained by a screw, a
lever, or any similar agency, and leave it thus until the metal has hardened; the
cliché is lastly separated therefrom and the metallic cast or mould thus obtained can
then be made use of, in the first place for taking therefrom proofs in transfer ink
for lithographic printing in the ordinary manner; or, in the second place, for metallic
blocks for typographic printing; or, in the third place, for the immediate production
of a galvanic inould in relief, from which may be taken at once galvanically any
number of sunk moulds for jewellery of any size, or for copper-plate printing, neither
moulds or casts requiring any re-touching.
According to the hardness of the cast required the proportion of the tin or of
the lead in the d'Arcet metal may vary from 5 to 20 per cent. each.
For the purpose of producing signboards, door plates, or other similar plates
replacing the usual engraved plates, I also make use of a solution of bitumen
instead of gelatine as above stated, in which case the bitumen is coated on a brass
:

page_text: F
plate, after sufficient exposure to light, in contact with the photographic negative, it
is developed in spirits of turpentine, washed in an abundance of water, and then
immersed in a galvanic bath, the nature of the metal contained in which will vary
according to the requirements; the unsolarised bitumen being then separated from
the plate this latter is lastly immersed for a few minutes in a solution of ammoniacal
carbonate of copper, or if it is desired to deepen the inscriptions in the plate it must
be placed for a few minutes in a solution of salt of copper, slightly acid, before
producing the above-mentioned re action by means of the ammoniacal salt.
Having now described and particularly set forth the nature of the said Invention
and the manner of carrying the same into effect, I would have it understood that I
claim as my Invention,―
Firstly. The method above described of preparing a bichromated gelatinous
negative so as to produce a grain on the proofs to be taken therefrom by uniformly
dusting on a glass plate an opaque powder, covering the same with a carbon paper
coated with a coloured bichromated gelatine, and then exposing the same to light,
applying the same under water to the negative previously coated with gum con-
taining a trace of chromic salt, and then developing it in tepid water, which carries
off the gelatine that has not been acted on by the light, leaving the insoluble
parts thereof forming the required grain, in the shape of an exceedingly fine pellicle,
adhering to the negative to be printed from.
Secondly. The process above described of swelling the gelatine negative, previous to
casting a mould from the same, by enclosing it for one or more hours in a box con-
taining damp blotting paper or fibrous material saturated with water, the said negativo
being isolated from the damp material by a few glass rods, and after extracting the
swollen negative from the box, coating it with finely pulverized plumbago.
Thirdly. The process above described of making metal casts from bichromated
gelatine negatives by the use of an alloy of metals fused at a low temperature, such
as a mixture of 1100 parts of d'Arcet metal containing bismuth in the proportion
of 1, tin 0.50, and lead 0.50, with 100 parts of mercury, the lead and tin ingredients
varying in the proportion of 5 to 20 per cent., according to the hardness of the cast
required as above described.
And, Fourthly. The process above described for producing signboards, door plates,
or other similar engraved metallic plates, by using bitumen coated on a brass plate
exposed to light under a negative, and then developed in spirits of turpentine,
washed in an abundance of water, and immersed in a galvanic bath, and after
separating the bitumen from the galvanic plate immersing the latter for a few
minutes in a solution of ammoniacal carbonate of copper, and if desired, to deopen
the engraving on or in the plate, inserting the same for a few minutes in a solution
of salt of copper, slightly acid, before producing the above-mentioned re-action by
means of the ammoniacal salt.
In witness whereof, I, the said Alfred Michaud, have hereunto set my hand and
senl, this Thirteenth day of November, in the year of our Lord One thousand
sight hundred and savanter nimhi
Witnesses,
D. H. BRANDON,
1, Rue Laffitte,
Paris.
R. H. BRANDON,
1, Rue Laffitte,
Paris.
A. MICHAUD. (L.B.)