It is now thirteen years since I had the honor of introducing in
France my new photoglyptic process, which, up to the present time, has
remained in the hands of very few, owing to the great expense hitherto
necessary to start the working of it. For some time I have been
engaged in making experiments with a view to discover a system which
should be at the same time simple and inexpensive; and the process
which I have this evening the honor to bring before your notice is the
result of my researches.
The summary of the new system is as follows:
To obtain from negatives reliefs on glass similar to transparencies by
the carbon process, but modified in the quantity of materials used.
To attach, and keep in absolute contact with the relief so obtained, a
sheet of tin foil.
To solidify this sheet of tinfoil by coating it with copper; then
backing it up with another sheet of plate glass covered with a
composition; and then to detach the whole from the first relief--the
result being a mould ready to place in the press and print one
thousand or more proofs.
I commence by showing you the relief made from the negative, and
explaining how this is obtained.
I take a sheet of plate glass of a convenient size, and place it in
hot water, together with a sheet of paper a little smaller; then,
having driven out the excess of water by means of a squeegee, I
place it on a leveling stand. Having prepared a solution composed of
gelatine 200 parts, water 1,000 parts, glycerine 20 parts, white sugar
30 parts, with a little Indian ink, and filtered the same, I pour a
sufficient quantity on the paper and spread it up to the corners with
the finger. These plates are then dried in a dry place and can be kept
until wanted.
To sensitize the plates I employ a bath of bichromate of potash of
six per cent., and again dry them. Without doubt this method is rather
long; but one should consider that each proof made is capable of
giving five or ten thousand prints if necessary, as the same relief
will make many printing moulds. I tried, with the aid of the Autotype
Company, of London, to get a suitable tissue; but as this requires
a uniform thickness of half a millimeter the ordinary system did not
succeed. When the sensitized plate is dry the edges are cut with a
knife, the glasses serving over and over again. I show you a piece of
this prepared paper.
As in the carbon process, it is necessary to place a border of black
paper at the back of the negative, and to cut the sensitized tissue a
little larger than the opening.
After the exposure the gelatine is fixed on a collodionized glass by
placing them both in water and squeegeeing the surface; but in dry
weather it is as well to use albumen in place of collodion, as used
by M. Ferrier for his transparencies in carbon. The glass holding the
gelatine is now placed in a hot water bath heated to 42 deg. Centigrade,
and left till the paper comes away from the gelatine, when it is
placed in this apparatus by the frame holding the grooves.
By means of this small gas regulator the temperature is kept always
the same, namely, 50 deg. Centigrade. The water should be now and then
agitated by lifting up and down the frame holding the glasses.
After a space of three or four hours the reliefs will be sufficiently
washed, and can be taken out and placed in alcohol to dry quickly
and sharp at the same time. In this stage of the process all spots or
scratches that may have been on the negative can be removed (being in
relief on the gelatine) by means of a piece of glass. The relief is
now ready to be covered with the tin. You will observe that up to the
present the operations have been almost the same as those necessary to
produce a transparency in carbon.
As it is of the first necessity that the tin should be kept in
absolute contact with the gelatine relief, I prepare the latter by
rubbing it over with a piece of flannel charged with a greasy matter
(pomatum answers as well as anything). I then make a border of
India-rubber in benzine round the glass. The effect of this is to
prevent any air from returning between the tin and the relief when
once it has been driven out.
Taking care that the back of the glass is perfectly clean, it is now
placed on the steel or glass bed of a rolling-press. A sheet of tin
foil (without holes) that has been smoothed on a sheet of glass by a
soft brush is now laid on it, and then three or four thicknesses of
blotting paper. The whole is then passed under the cylinder several
times, each time increasing the pressure. The surface of the tin
is now ready to place in the electrotyping cell, but must first be
cleaned with a solution of caustic potash to remove any grease, and
bordered with shellac varnish to prevent the copper from depositing
where not required.
Electric contact is made by means of the small apparatus, on removing
a small proportion of the lac varnish. After two or three hours
sufficient copper will have been deposited, and after drying can be
then attached to another glass, on which it will remain.
This glass is covered while hot with a composition of shellac, resin,
and Venice turpentine, and can be prepared in advance, using an iron
plate heated direct by the gas flame. The same iron plate is employed
to again soften the composition and attach it to the copper; but this
time heated only by boiling water, this temperature being sufficient
to soften it until it enters into all the hollows of the copper. On
placing a weight on the two glasses the excess of the composition is
forced out at the edges. When cold the glass plate on which the copper
and tin are now attached can be separated from the relief, which can
then be used over and over again to produce fresh matrices.
The matrix or intaglio is now ready to place in the printing press,
and the remaining operations of printing are exactly the same as those
used in the old process of photoglyptic printing.
In placing the mould in the press it is advisable to place one or
two thicknesses of stout blotting paper, previously wetted, under the
mould to give to it a slight amount of elasticity and, at the same
time, to keep it in place.
As in all other mechanical processes a reversed or pellicle negative
is required; but it is very simple to print upon a specially prepared
transfer paper, and, instead of mounting the print with the face
uppermost, to attach it under water to the mount, and when dry to
detach the paper on which the print has been made. By this means there
remains only one thickness of paper instead of two, thus doing away
with an objection which has often been found in mounted photographs
for book illustration.
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