Polymer Photogravure is a process of producing a photographic image from a printing plate with etching inks on 100% cotton rag papers. It has an archival quality of several hundred years.
There are two methods of printing from a plate: relief printing and intaglio printing. Relief printing or lithographic printing prints the surface of the plate. Intaglio printing prints what has been etched into the plate. In relief printing a roller rolls ink across the plate and is then transferred to paper. In intaglio printing the surface of the plate is covered with ink, then removed by wiping the surface of the plate and then pressing the plate through a press onto paper.
A photograph printed in relief has dots of varying size: a highlight will have very small dots, and a shadow will have large dots. In gravure printing all the dots are the same size but are etched either deeper or shallower into the plate. In a shadow area there is more ink and a highlight area has less ink. The uniqueness of intaglio gravure printing is the velvety lush quality of the ink.
Traditional copper plate photogravure developed in the late 19th century immortalized many of the early photographic masters: Paul Strand, Alfred Stieglitz, Alvin Langdon Coburn, Edward Steichen and Edward Curtis. The process was done by Photogravure printing companies. It was extremely time consuming, highly caustic and involved the use of ferric chloride acids, ground asphaltum, carbon tissue and ‘devils blood’. The results, however, were mesmerizing.
In the 1980s photopolymer plates were developed for the Flexography printing trade as a method of letterpress printing producing long runs and safer, more cost efficient techniques. Printing was done in relief for the offset industry. As is often the case artists realized the process could be done in intaglio and evolved to solar plates: exposure to the sun. The polymer in solar plates is coarse and exhibits a grainy image. Polymer Photogravure plates have a finer grain structure and create better detail.
There are three processes necessary for making the plate: preparation of a positive photographic image on film, exposure via ultra violet light through the positive onto the plate and a second exposure to a fine line dot screen. The preparation of the positive may be done in traditional photographic methods in a dark room by exposure to film rather than paper; however, the latitudes necessary for the contrast levels must employ the use of a densitometer. The more convenient and contemporary method is via a computer in Adobe Photoshop. A digital image or scanned photographic image is adjusted for contrast control and printed on OHP Transparency Film. This is a film that absorbs inkjet inks in 2880 dpi in black and white.
The plate preparation involves two exposures: one to the positive and one to a stochastic dot screen created by the computer through diffusion dither bitmapping. The stochastic screen can be purchased and is similar to a mezzotint screen. The purpose of the stochastic screen is to hold a dot pattern in the shadow areas when the plate is wiped; otherwise the ink would be wiped out.
I employ a mercury vapor lamp for the ultra violet exposure and use a glassless vacuum frame to hold the films in intimate contact with the plate. Once the exposures are made the plate is washed out in water with a soft brush. The plate is then dried and post exposed in the ultra violet light to harden the polymer.
Once the plate is made traditional etching techniques are employed to print the plate. Ink consistencies and a variety of ink colors can be used to alter the color of the print. Acid free etching or watercolor papers of 100% cotton rag need to be pre-soaked to soften the cotton fibers to absorb inks. Wiping techniques, press pressure, felt size catcher and pusher blankets can greatly affect the quality of the prints. Once the prints are made they need to be dried with cotton rag blotter papers to ensure their flatness and absence of acids under glass with weights and exchanged every few days.
The richness and timeless qualities of the finished prints are unsurpassed to other forms of photographic printing. Moreover, the use of 100% cotton rag papers and linseed oil inks make the archival quality of the prints ageless. The final print reveals the embossing of the plate as well as the watermark of the paper and chop marks employed by the printer. Also, the deckled edges exhibit a unique, one of a kind print.
CRIS PULOS