IMPROVEMENTS IN OBTAINING PHOTOGRAPHIC PRINTING SURFACES
Year: 1884

page_text: I, JOHN ROBERT SAWYER Director of the Autotype Works Ealing Dene
London W do hereby declare the nature of my invention for IMPROVEMENTS IN
OBTAINING PHOTOGRAPHIC PRINTING SURFACES to be as follows:-
In the method of Photographic Engraving from a Gelatine relief developed on a
metal plate, great difficulty and uncertainty of working has arisen from two causes.
One, being the difficulty of rendering the surface of the gelatine relief a sufficiently
good conductor of Electricity, another, being the impossibility of obtaining a
suitable grain or tooth upon the Electrotype so as to enable it to hold printing ink
in exact relation to the lights and shades of the Negative from which the original
relief has been printed.
These difficulties I have overcome by employing in the manufacture of the
pigmented paper or Tissue employed in the production of the relief, that form of
Carbon known as Amorphous Graphite, which being ground into the Gelatine used
for making the Tissue, gives in the developed picture an even and regular grain,
exactly proportioned to the varying depths of light and shade produced by the
original negative, and at the same time renders not only the surface, but also the
whole of the relief conductive of Electricity.
The Tissue may be made by any of the ordinary published methods, I find that
5 per cent of Graphite to a 40 per cent gelatinous solution forms a very good
working proportion, the Tissue may be made sensitive to the light at the time of
manufacture, or may be sensitized, afterwards by immersion in a solution. of
granulated Bichromate of Potash of a strength of five per cent.
The printing is conducted in exactly the same manner as for autotypes on
carbon prints, but the developement takes place upon a sheet of polished silvered
copper; after development the picture is rinsed in cold water and then placed in a
five per cent solution of common alum for half an hour, it is then thoroughly
washed and allowed to become perfectly dry.
The next step is to polish the surface with a brush similar to a small cloth brush,
in such a manner as to secure a perfectly even black polish over the whole of the
surface of the relief, when this occurs the relief is ready for the Electrotyping Vat,

page_text: The Electrotyping is carried on in the usual manner, the copper plate bearing the
relief being placed in proper electrical circuit opposite to an anode of suitable size;
if the connections have been properly made, a few minutes will suffice to deposite
a thin coating of Electro Copper on the gelatine relief, and a few days more or less,
according to the strength of the Battery or Dynamo employed, will suffice to
produce a copper plate of workable thickness, when this result is attained, the
adhering plates are taken from the Vat, filed round their edges & separated; it will
then be found that the Electrotyped plate has upon its surface a inost delicate &
perfect relief, which upon being placed in the hands of a skilled copper plate
printer will give a picture showing all the gradations of light & shade to be found
in the original negative.

page_text: I, JONN. ROBERT SAWYER, Director of the Autotype Works Ealing Dene
London W. do hereby declare the nature of my invention for IMPROVEMENTS IN
OBTAINING PHOTOGRAPHIC PRINTING SURFACES and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement:―
My invention relates to a process of photographic Engraving in which a photo-
graphic picture in pigmented Gelatine, made sensitive to the action of Light by.
means of Bichromate of Potash, or Ammonia, is developed upon a polished copper
plate; the surface of this picture being rendered electrically conductive, it is placed
in a depositing vat in proper electrical connection with a suitable anode, and
copper deposited upon it until the deposited copper attains the thickness of an
engraver's plate; as soon as this is accomplished the two adherent plates may be
separated and the deposited copper plate will be found to bear upon its surface an
exact reverse copy of the Gelatine photograph as developed on the original copper
plato.
In this process the photograph is formed of masses of gelatine and pigments
varying in thickness according to the degrees of light and shade in the original
photographic negative or cliché, and being developed upon the rigid surface of the
copper plate it is necessarily in relief, the various elevations and depressions
corresponding to the lights and shades presented by the negative from which it
has been printed; the highest clevations forming the deepest shadows whilst the
various grades of depressions correspond to the half tones, the high lights being
represented by depressions going down to the surface of the Copper.
If the surface of the picture thus described is rendered electrically conductive
and copper deposited upon it in sufficient thickness to form a plate, when the two
are separated it will be found that the deposited copper plate bears upon its
surface an exact copy of the gelatine relief but with this difference that it is in
intaglio where the gelatine was in relief, the elevations now forming the high
lights whilst the depressions constitute the shadows and half tones of the picturo.
A copper plate thus produced, so much resembles an etched or mezzotint plate as
to raise hopes that it could be printed from by a Copper plate priuter and it can be
inked with printing ink and a dabber with perfect facility, but here arises a
difficulty, that when the plate is wiped and cleaned off as is the practise in copper
plate printing, the ink wipes entirely out of the plate, thus rendering it impossible
to print satisfactory proofs; this arises because of the absence of a tooth or grain
having ink holding power.
In practise there is also another difficulty, and that is, the coating of the gelatine
surface of the relief so perfectly with a good electrical conductor as to ensure the
deposition of a thin film of copper over the whole of the surface before the acid
fluid of the electrotyping vat has had time to attack and swell the gelatine, for
should this take place the electrotype will be entirely useless.
These difficulties I claim to have overcome by introducing into the gelatine
employed to make the original relief, a substance capable of being treated so as to

page_text: give grained surfaces of different degrees of fineness or coarseness, and which at
the same time is a very good conductor of Electricity; this substance is known as
Amorphous Graphite, and my method of employing it is as follows.
Amorphous Graphite can be purchased in fine powder as levigated plumbago;
I take a quantity of this and pass as much as I can through a brass sievo 120 holes
to the inch, all that will pass through the meshes of this sieve I put aside for
pictures requiring the finest grain, I now pass as much as I can of the remainder
through a sieve with 80 holes to the inch, this I put aside for a medium grain, and
pass what I can of the residue through a sieve with 40 holes to the inch, this is
put asido to make the coarsest grain; whatever plumbago now remains is preserved
and reground. I thus secure Powdered Graphite of three different degrees of
fineness; the finest I eniploy for line work and for very small and delicate pictures,
the medium for larger pictures up to about 15 inches, whilst the coarse grain is
necessary for large bold work, copies of oil paintings, and subjects in which largo
size and vigour of treatment is desirable or necessary.
Having obtained the Graphite in the degrees of finoness that experience has
shown me to produce the best effects in the various classes of work for which this
process is suitable, the next step is to get them into intimate admixture with the
gelatinous compound in which the photographic relief is to be made.
To this end I take Gelatino 40 parts, Loaf Sugar 6 parts, Carbolic Acid a trace,
and water. 100 parts.
It is difficult to exactly specify the sort of gelatine best suited, I have found
some of the best foreign gelatines in thin white sheets answer very well, but on.
the whole I think the gelatine manufactured by. Messa Nelson Dale & Co and
known as No.3 finke gelatine, to be the best adapted to this purpose.
Having decided upon the Gelatine to be employed, I soak it in the specified
quantity of cold water in which the sugar has been previously dissolved; I now
apply gentle heat until the gelatine is all melted, then adding the carbolic acid the
mass is churned vigorously for an hour, employing for this purpose one of Kents
Albumen Churns, it is now allowed to cool, in a few hours the froth will have
subsided and the mass will subsequently become a firm Jelly, when it is ready
for use.
The quantity. to be taken of this Jelly will of course depend upon the magnitude
of the operations; but supposing three pounds is taken, I weigh out three ounces
of whichever grade of graphite powder I consider will best answer for the kind of
work to be attempted; the three pounds of Jelly are melted in a tin can surrounded
with hot water, and the three ounces of Graphite added with stirring; in order to
secure the most perfect admixture, I pass the whole through a mill such as is used
in grinding paint.
The next operation is to coat paper. with this compound; there are several 4
modes of doing this, in manufacturing on a large scale, I employ the machine
described by Messrs Swan and Johnson in their lapsed Carbon printing patents.
For operations on a small scale, the following will be found to be a convenient
mode of procedure, obtain a semi-circular tin trough say 24 inches long, 6 inches
wide and 4 inches deep, it will be convenient if this is made with flanges one inch 4
in breadth at the sides and ends, so that it will rest upon the edges of a tin box
made a little larger than the trough; this when filled with warm water will prevent
the gelatinous compound becoming chilled in the process of manipulating.
Next cut strips of paper, ordinary printing paper answers very well, and can be
had in long lengths; the strips of paper may be any width up to 22 inches and 5
should be about five feet in length; now pub some warm water in the tin box, put
the trough in position and pour in the gelatinous mixture; it will now require
skimning by passing pieces of folded paper over the surface from end to end, and
removing every particle of froth and getting rid entirely of air bubbles; when
this is accomplished, make one of the strips of paper into a loose roll and placing 5
the trough on the ground take hold of the free edges of the roll of paper with the
finger and thumb of each band, and place, the roll gently on the surface of the

page_text: gelatine in the trough, now draw it upwards slowly in a vertical direction, the
paper will unroll itself upon the gelatinous compound, and if the operation has
been dexteriously performed will be coated very evenly on one side only; on
leaving the trough the paper should be waved backwards and forwards through
the air to cause the gelatine to set, and it may then be hung up to dry; in this
condition it may be kept for any length of time, when required for use it must be
made sensitive to Light by immersion in a four per cent solution of granulated
Bichromate of Potash, and then allowed to dry in a dark well ventilated apartment
in the same way as the ordinary Carbon Tissue is dried. If it is desired to have
the Graphite Tissue sensitive to Light when first made, all that is necessary is to add
to the 3 lbs. of gelatinous compound 2 ounces of granulated bichromate of potash,
and allow the strips of paper after coating to dry in a dark and well ventilated
apartment; the tissue so made sensitive will not remain good for use more than a
few days but will gradually become insoluble; both kinds are best preserved in a
closely fitting tin case, and in as cool a room as can be obtained.
The printing is carried on in exactly the same way as Carbon Printing, the
tissue is cut into suitable sized pieces, placed upon the negatives in pressure
frames, and exposed to Light, the time of exposure being judged by the actinomoter.;
when the picture is judged to be sufficiently exposed it is retired from the pressure
frame and immersed in water as cold as possible, in Summer the use of Ice is
advisable; when the piece of tissue just unrolls itself, it is taken out of the water
and laid face downwards upon the surface of a polished copper plate; the surface
of this plate may have been coated with silver by means of Electrotype or
immersion in Cyanide of silver solution, but this is not indispensable; the piece of
tissue must now be forced into intimate contact with the surface of the plate by
an instrument known as a squeegee, it is then put aside for a few minutes when
it will be ready to develope in warm water; all these operations are perfectly well
known and present no difficulties to the Carbon Printer. If the exposure has been
correct, the picture will appear upon the Copper Plate as an exquisite relief, with
the lights and shades gradated in the most perfect manner, it is now well rinsed
in cold water, then placed in a solution of alum four or five per cent for ten
minutes, is again rinsed with cold water and allowed to dry spontaneously.
On examining the picture when dry it will be found that the deepest shadows
are represented by masses of Gelatine, the highest lights, on the contrary being
the bare surface of the copper plate; an examination with a magnifying lens will
also shew that the surface is covered with a grain, that this grain varies in quantity
with the varying grades of the picture, very little being observable in the lightest
shades, none at all in the highest lights, and in great quantity in the deep shadows.
The next operation is to render this surface electrically conductive, this is a
particularly easy matter, as the whole of the picture is permented in every part
with the Graphite which is a very good electrical conductor; all that is necessary
is to polish the surface with a suitable brush, a hat brush answers perfectly well,
and there will be no difficulty in obtaining a fine black polish, especially if the
brush be just drawn over the surface of a block of Plumbago from time to time.
When an even polish is obtained upon the surface of the Relicf it is ready for
the Electrotyping vat; it is a good plan to solder a strip of copper to cach of the
four edges of the plate, so as to be able to suspend the plate from the electrical
connections by any one of these, and change the position of the plate whenever
necessary; by this means the streaks that are likely to appear when the plate is
first placed in the bath can be got rid of.
The plate is next covered at the back with sholi lac varnish, to prevent the
deposition of Copper on the back of the plate, the copper strips are also thus coated,
all except that portion which is to form the contact with the electrical current,
this portion must be kept bright and clean. It is now placed in the Electrotype
Vat containing an acid solution of Sulphate of Copper of the ordinary strength used
for the deposition of Copper, suspended from the vat connections by one of the
Copper Strips, and a copper anode of about the same size suspended opposite to it ;
"

page_text: in a few minutes it can be lifted out and examined, if the apparatus is in working
order, a film of copper will have been deposited upon the Relief, it is now returned
to the vat, but this time suspended by a strip from a different edge of the plate;
it is well to change the position of the plate four times in this way during the
first hour.
This process of electro deposition is one that can only be carried out successfully
by persons accustomed to such work, the copper can be deposited either by means
of battery power or by a Dynamo Plating Machine driven by Steam Power, but in
either case practise and experience can alone regulate the strength of the current,
the position of the Cathode and Anode, strength and temperature of the solutions,
and the general electrical organisation.
It is as well to weigh the copper plate bearing the relief before it goes into the
vat; after the lapse of a few days, a substantial coating of copper will be observed
to have taken place, the plate may now be weighed, and if it weighs more than as
much again as the original weight, it may be retired from tho vat, washed in cold
and allowed to dry.
The Copper strips should now be taken off, the partially loose growth of copper
round the edges broken away, and the edges of two adherent plates filed all round;
when this is done, the junction line of the two will be observed, a thin knife
should be gently inserted and with a little care the two plates may be separated.
It will now be found that the electrotyped plate has upon its surface a perfect
reverse copy of the original gelatine picture, the graphite forming the grain being
reproduced in the Copper and now forming the inkholding feature of the Electrically
deposited plate; it is now ready for cleaning, trimming and bevelling the edges,
when it will be ready for the copper plate printer, who will be able to ink, wipe
and print it in just the same manner as he would a mezzotint or engraved plate of
the ordinary kind.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
1° The introduction of Amorphous Graphite otherwise known as Plumbago, into
a Compound of Gelatine, sugar and water in the proportions indicated, for the
purpose of coating paper and forming a tissue; this when made sensitive to the
action of light, may be printed under a photographic negative, and a picture in
relief formed having by virtue of the graphite employed a grain in proportion to
the lights and shades of the negative, and also by virtue of the electrical conducting
power of the Graphite, be capable of receiving a deposit of Copper by means of
electrical action.
2° The separating of the Graphite into grains of different sizes, which when
introduced into the gelatinous compound, will give the Reliefs grain of different
sizes to suit the various dimensions and styles of work for which the process may
be employed.