Re: Photopolymer Photo Gravure Press Questions
"Dwell time"....Great phrase, Jack! Your words are probably the best technical description I've read with regards to the reason why a wide drum diameter is more effective Jack. I'd like to work your descriptions into my on-line documentation about polymer photogravure, with your permission. I'll edit somewhat, of course. Please see http://intaglioeditions.com/procedures/polymer_photogravure.html and let me know, off line.
Other types of intaglio printmaking such as traditional spit-bite etching, drypoint, even monotypes, all require considerably less pressure than anything with a fine enough dot where you're trying to achieve continuous tone. Smaller presses with smaller drums will work, but I've found myself lifting the things off the ground while cranking in an attempt to get a larger plates through at the pressure required to get smooth, continuous tone. Not fun for the rotary cuff, nor when the crank recoils and hits your forearm. Ouch. Much better ways to skin a cat.
I should say, some approaches to photogravure - traditional and with polymer plates - use a very coarse aquatint that looks akin to Tri-X pushed 3 stops. This is not the kind of photogravure I'm talking about when I say it requires near-extreme pressure. A typical, coarse aquatint is more forgiving and requires less pressure - but produces far fewer gray tones to the eye. A very fine aquatint - one that produces 100 distinct steps - requires much greater pressure to pull an acceptable print - more than any other type of intaglio printmaking I've come across.
Jack Brubaker wrote:
Jon, The fact that a smaller diameter makes a narrower line of contact is the reason for more pressure on the plate (per square in.) with the same pressure on the adjusting screws and frame. The wider line of pressure with a larger roller gives more dwell time during which the paper can get into the recesses of the plate and bond with the ink. Dwell time can also be extended with slower travel time through the press. Is it your experience that a photogravure needs more pressure than other intaglio plates might need? Jack
-- Jon Lybrook Intaglio Editions http://intaglioeditions.com 303-818-5187