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About Etchings & Engravings
In the world of printing and print making, almost all methods fall under one of 3 basic headings, Relief, Planographic and Intaglio. The latter method, "Intaglio", is the collective term for the the print making techniques that encompass engraving and etching.
The other forms of printmaking fall into two
basic groups. "Relief" (which includes letterpress
and woodblock printing) involves printing from a raised surface
(the opposite to Intaglio) and lacks the inherent ability to render
tones of varying strength (a raised surface cannot be "more
raised") the other is "Planographic" (including
various types of Lithography, as used in most commercial book &
magazine printing and for most other art prints) where the image
area sits on the same level as the non image areas, but has some
different property (usually water repellent as opposed to water
receptive.) Most methods in this group also lack the inherent
tonal capability of Intaglio. It's
distinction and the feature responsible for such "depth of tone" is that the
image on the plate is formed by lines and crevices cut below the surface rather
than by an image raised above the rest of the printing plate (as in relief) or
by different surface properties (as in
The highly skilled engraver uses the burin to cut an image, as a
series of lines of varying width and depth, that are a translation of the tones
and shadings of the artists original work. Deep lines hold more ink than shallow
ones, producing a darker tone when printed.
At this stage, the softness of the metal, means that the image is vulnerable to rapid wear from the wiping which is an integral part of intaglio printing. For this reason, during a period in the history of intaglio printmaking, many engravings were produced on steel rather than copper plates, which are much more durable by virtue of greater hardness of the metal. This hardness however, makes the task of the engraver very much more difficult, and restricts his style, by reducing his "freedom of expression".
The problem of rapid wear of copper engravings, together with the difficulty of engraving on steel, was solved in the late 1850's with the invention in France of the process of "steel facing". This revolutionary technique, a special form of the then new discovery of electro-plating, enables a very thin "skin" of steel (less than two ten-thousands of an inch) to be applied to an engraved or etched copper plate, imparting the hardness of steel to the engravers favourite metal of choice. Since it's invention, some one hundred and forty years ago, most engraved plates have been made on copper, and steel faced for protection from wear. Steel facing is used to this day, and is an essential part of preserving valuable copper plates, while still enabling them to be printed for all to enjoy.
G.E. (Gravure etching, or Photogravure)
Gravure etching was probably the final revolution in intaglio publishing. Discovered by Nicephore Niepce in 1827, research into the method was continued by Fox-Talbot in the 1850s from where the subject did not really progress until it was finally developed commercially in the 1880s.
The process involves the use of a light sensitive gelatin which is applied to the copper plate. A positive image of the design to be etched is then placed in contact with the gelatin and then exposed. The special properties the gelatin ensure that where much light is received (the light areas of the design), the gelatin hardens, and remains softer in areas where less light is received.
The gelatin is then washed with water and the softer parts are dissolved away. The plate with the hardened gelatin is then placed in an acid bath and the acid gradually eats away at the gelatin surface and consequently the plate. Those areas of the gelatin that remained soft from exposure are relatively unresistant to the acid and so allow the plate to be etched fairly soon into the etching process; these are the darker areas of the plate which will consequently hold more ink. The areas of gelatin which received much light will remain hard throughout the etching and will only let acid onto the plate towards the end, or perhaps not at all; in these areas ink will not be held in any great quantity, if at all, and therefore will be very light or white in the corresponding impression.
The gravure etching process is extremely difficult, more of a craft skill than the art of an engraver, demanding in the etcher a unique knowledge and feel for the length of time that the plate must remain in the acid bath: too long and the plate will produce prints with too much contrast, too short and the prints will have a grey appearance. Often it can take several attempts and wasted plates before a satisfactory result is achieved. Various highlights will be added by selective wiping of the acid across the plate and by further work on the plate with a burnisher or burin.
A very detailed description of the process of photogravure can be found here at the website for The Kamakura Print Collection.
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