By Elmer Latham.
The method by which a photogravure plate is produced, is probably the
least understood of all of the many photo-processes of reproduction.
This is chiefly on account of the difficulty of the process, which is
not an easy matter to explain in detail, and also on account of the
secrecy with which all plate makers guard their processes.
The reproduction of a mezzotint or line-engraved print, when made by a
good photogravure process, produces in most cases a print which cannot
be detected from the original. The originator of the process was
probably Fox Talbot, an Englishman. The writer has seen one of his
prints, made between 1855 and 1860, which was a very creditable piece
of work. Dujardin of Paris took up Talbot's process, and after much
modification, succeeded in developing a successful process which he is
working to-day. All photogravure plate makers of the present time have
more or less copied the process of Fox Talbot.
There are three different methods of making these plates known to the
writer. The reader probably knows that a photogravure plate is not a
relief plate, but an intaglio, and is printed on an etching-press in
the same manner as an etching and requires special skill in printing
on the part of the printer to produce the best results. I will give a
brief explanation of the three different processes.
The first is known as the transfer process. In this process a reversed
photographic negative is made from the copy, from which a positive or
"transparency" is made, either by contact or in the camera. A piece of
carbon paper is then coated lightly with gelatine, sensitized with
bichromate of potassium and allowed to dry. The paper is then placed
in contact with the positive and printed in daylight until the image
is imprinted on the gelatine coating of the paper, such portions of
which as have received the most exposure from the action of light
becoming quite insoluble. A copper plate, cleaned so that it is free
from grease, is introduced into a large box into which has been blown
a very finely powdered resin, which is allowed to settle somewhat
before putting in the plate. The plate is allowed to remain in the box
until a fine deposit of resin has settled all over it. It is then
carefully removed and heated over a gas burner until the resin adheres
firmly to the plate. The resin is melted only to such a point that it
forms a fine grain all over the plate, leaving interstices of bare
copper between. The paper, on the gelatine surface of which the
picture is printed, is now placed in a tray of warm water, and the
parts of the image which have had the least exposure are thereby
dissolved and washed away, the image being thus fully developed on the
paper. This is placed in contact with the grained plate, which has
been placed in the tray of water, and firmly squeezed in contact with
the plate. The paper is stripped off, leaving the gelatine film on the
copper. The plate is now removed from the tray and dried, and is then
ready for etching, which is accomplished by placing the plate
successively in several baths of acid of different strengths until the
desired results are obtained. This process gives a shallow plate, of
not great wearing quality, and, as a rule, requires a great deal of
work by the engraver to bring the plate up to anything like the copy.
The light tints come out very soft and smooth, but the black tones
etch "flat" and lose all detail. These blacks must be put in by hand.
The poor wearing qualities of these plates make them undesirable in
cases where a large edition has to be printed.
The next process is the "deposited" plate used by "Goupil" of Paris,
in which copper is deposited by electricity upon a swelled gelatine
film which has had a grain formed upon its surface chemically or
otherwise. The deposition has to be continued until the plate has
acquired the necessary thickness, which takes about three weeks; and
this is a long time to wait in these days, when a publisher usually
expects his order executed in ten days. These plates are practically
hand made. The process gives a plate that could not possibly be used
without a great deal of retouching by an expert engraver. Goupil turns
out a beautiful plate, due principally to his large force of
engravers, one man working on a particular part of the plate, then
passing it on to another who does some other portion, and so on, until
the plate is finished. In this way each engraver becomes exceedingly
skilful in one thing. Line engraving is reproduced by this process
exceedingly well, but such plates, like the transfer process, are
shallow and give out soon in the printing.
The last process that I have to deal with is the one I am working
myself. In this process the plates are made in two or more etchings,
according to the requirements of the subject which is to be
reproduced. This method produces a plate of great depth both in the
light and black tints, and on account of the small amount of hand-work
required after the plate is etched, the copy is followed very closely.
With a good positive and favorable conditions, quite frequently a
plate is made upon which the retoucher needs to do no work at all, and
a more faithful reproduction is made than by any of the other methods
that I have mentioned. After a good positive is procured, the copper
plate is cleaned, and a sensitized solution of gelatine is flowed over
the plate, dried down, and then printed under the positive, with a
short exposure. The plate is grained as in the transfer process, and
is then etched.
This first etching, on account of the short exposure, goes over the
plate in about three minutes, and is simply intended to get the light
tints. The plate is again cleaned off and coated, this time in a
different manner, and given a much longer exposure under the positive.
The next etching takes about three hours, which gives the blacks great
depth. Comparing this with the transfer plate which has an etching of
from fifteen to twenty minutes, the reason for the difference in the
wearing qualities of the plate is quite evident. This process, whether
used by myself or others, I feel free to say is the best one that has
ever been worked, inasmuch as it gives a far more faithful
reproduction than any of the others with a minimum of work by the
retoucher.
Some plate makers claim to make all their plates without any
retouching, which cannot be done. As I have mentioned before,
occasionally a plate can be made as good as the copy without
hand-work. But to say that any chemical process gives such results
continually, or that a plate cannot be improved by a skilful retoucher
is, to say the least, misleading. All of the different processes are
very sensitive to atmospheric influences, and no small amount of
chemical as well as mechanical skill is required to keep things
running smoothly; and at certain times the best of operators are at a
loss to remedy some slight fault that may upset things temporarily.
Photogravure making is based upon a foundation of small details, that
must be looked after with the utmost care, and the neglect of any one
of which means failure at the end. So it may be surmised that at times
the operator has trouble of his own.
Every maker of plates, no matter which process he uses, has his
individual ways of doing things, so that except in a general way no
two processes are operated alike. This gives an individuality to each
man's work, and an expert can easily tell one from another. For
high-class illustrations, no other photographic process can compare
with photogravure, and no doubt it will be many years before anything
will be found to excel or even equal it. Much experimenting has been
done with other methods, but the results have always been inferior,
and I think it is safe to predict that the photogravure will always be
popular.
Etchings, mezzotints, and steel engravings are still occasionally used
in the illustration of fine books, and brief descriptions of how they
are made will be of interest.
An etching is usually made on a copper plate. The plate being covered
with a thin coating of wax, the artist works on it with an etching
point, sketching his subject on the plate in fine lines as he would in
making a pen-and-ink drawing, but cutting his lines through to the
copper. The plate is then "walled in" with a high rim of wax, forming
a sort of tray of the plate. Into this tray is poured a diluted
solution of nitric acid, which etches, or "bites," into the uncovered
lines on the plate. Some artists give a plate a short "bite," as the
etching is called, for the light lines, then cover these portions of
the plate with wax and give the plate successive "bites," stopping out
each part as it gains its required depth. Others remove the coating
and "prove" the plate by taking a print from it after each
"bite,"--each of these prints being known as a "state of the plate"
and showing what is still required to be done. In the work of an
etcher like Whistler the impressions of the "first state," "second
state," etc., are of considerable interest, as they show the progress
of the man's work, but, except as an object of interest or as a
curiosity, these prints can have no real value as they are unfinished
work, simply showing the various stages in the making of a work of
art.
A mezzotint is also usually made on a copper plate. A texture, or
groundwork, is worked on the copper plate with a tool resembling a
cabinet maker's toothed plane iron, except it is rounded at the end.
The teeth are very fine, ranging from forty to one hundred and twenty
to the inch in different tools. This tool is called a "Bercier," or
"rocker." The rounded edge allows the tool to be rocked across the
plate, the rocking motion causing the teeth to form indentations in
the copper. The rocking has to be continued until the surface of the
plate is completely covered, and it then presents an appearance like
velvet. Rocking in from forty to sixty directions is necessary to
cover the plate properly. The durability of a mezzotint plate depends
entirely upon the pressure put upon the rocker, and the depth to which
it penetrates the copper. After the ground is thus laid, the outline
is sketched in on the rocked surface, which takes the pencil easily,
and then with steel scrapers and burnishers the light and middle tints
are worked down, leaving undisturbed the portions of the surface where
the strongest blacks are to be. From time to time, a print is taken
from the plate, to note the progress of the work, which advances
slowly to the finish. On account of the length of time necessary for
the laying of the ground and the scraping of the plate, many artists
hesitate to attempt mezzotint plates. There are very few men in this
country to-day who do mezzotint engraving, which, considering the
results to be obtained, seems somewhat surprising.
For flesh tones, drapery, and landscapes it has no equal. The velvety
richness of the blacks, the beautiful gradations of the middle tones,
and the extreme delicacy of the light tints give the artist a power of
expression not obtainable by any other method of engraving. Besides
this, as the engraving is done on the bare copper, the artist can see
at all times the progress of his work without having to take off the
wax ground as he must in making an etching. This is a great advantage,
for as the effect of each stroke can be plainly seen on the plate, the
element of uncertainty which always attends the production of an
etching is entirely eliminated, and it is then simply a question of
skill with the scraper. The difficulty of obtaining rockers is one
great drawback. I doubt if one could be obtained in New York to-day.
The teeth have to be very accurately cut, and a perfect tool has a
value to an engraver that cannot well be estimated. The lack of demand
has prevented their manufacture in this country, but they could be
made here by any fine tool maker.
Steel engravings are still used to some extent in this country,
although only in portrait work. A wax ground is laid on the plate as
in etching. A tracing is made from the photograph, from which the
picture is to be made, and is then transferred to the wax ground. The
engraver then follows the lines of the tracing with an etching point,
the hair, head, and outline of the features being gone over carefully.
Then the plate is etched with weak nitric acid. If the face is to be
"stippled," it is covered with fine dots made by a graver directly on
the surface of the metal after the plate has been etched and the wax
cleaned off. If the face is to be a mezzotint, that part of the work
is all rocked over, and then scraped down within the etched outline,
when the flesh is modelled as in a regular mezzotint. The drapery,
background, etc., is usually done by a ruling machine with fine or
coarse, waved or straight lines, as the texture may require. These
lines are ruled through a coating of wax, and then, by etching and
stopping out, the required results are obtained.
This method of engraving is also giving place to process work, and in
a few years more the steel engraved portrait will probably be a thing
of the past.