What Is Polymer Photogravure Printing?

My choice of medium is an integral element of my vision. For Tongues Turned to Stone, I chose polymer photogravure, hand-made Japanese paper, and custom-mixed etching inks to give a vintage look that references the past. The paper is translucent, and the ink mixture is warm. This gives the appearance of parchment.

Photogravure is an intaglio printmaking procedure for producing an etching-ink image on paper from a photographic original. It exists in two basic forms: copperplate and polymer photogravure.

Copperplate is the historic process. It requires a gelatin-coated tissue paper that must be sensitized by soaking in potassium dichromate. After exposure to ultra-violet light, it is adhered to a copperplate, which is hardened to become a resist. Subsequent etching in ferric chloride yields an intaglio plate for printing.

I used polymer photogravure. The plates come pre-coated with an ultraviolet-sensitive polymer. The plate is exposed to a custom dot screen (aquatint screen) that gives a stochastic (random dot) pattern and results in a tooth or pit where ink is retained. The subsequent positive transparency image exposure removes the areas from the screen image that receive the most light and leaves the shadow areas with more ink.

I use a medium format digital camera (Pentax 645z) to produce color images. The images are converted to monochrome, tonally optimized, and enlarged to their final size in Photoshop.

A positive is printed on transparency with an Epson 9800 inkjet printer using Piezography inks. The positive image exposure, followed by the screen exposure, is done in contact with the plate in a vacuum frame using ultraviolet metal halide light. The polymer is hardened by UV light in proportion to the densities of the positive. The unexposed polymer is washed away in the developing step. A second bare UV exposure hardens the polymer further.

The plate is the inked with Charbonnel etching ink, which is retained in the intaglio pits after wiping the surface. The Gampi-shi hand-made, translucent paper is soaked in water, applied over the plate, and printed on my antique Griffin etching press.