Yes, you read that correctly: spit-bite. Contrary to what Wiki says, we are learning the old-school method, so it is what it sounds like– a way of “biting” the plate with acid that involves actual salivary effluvium– ergo: spit. (As has been said, Not everything counts as Art, but everything counts as Art Supplies). I was curious to learn and test this technique, so I decided to use it in the backgrounds of these two otherwise staid (and perhaps lifeless) portraits that I worked on last weekend.
First step (after the line work has been etched) is to coat the plate with a fine layer of powdered rosin (there are several ways to achieve this– I used the rosin box at the studio) for aquatint. Once the plate is covered, the rosin must be melted *just* enough to stick to the surface of the plate, but not so much that all the individual granules blob into a single waxy surface. Once this has been achieved, you have a textured ground upon which to work the process, of spit-biting to achieve tonal (v. linear) areas.
Next, to bring out the magically modeled tonalities, you work with undiluted acid (the bath is usually around 50% of full strength), and, of course, some spit– with a soft watercolor brush. You can have more control in this way than simply dipping the lot into a bath.
Proofs after spit-biting the aquatint. The people were masked with a sharpie to keep the acid off them.
The man’s background was done by my instructor (Fred Mershimer) in a demonstration to the class. I worked on the woman’s afterward. His looks great– my technique obviously needs practice! It came out rather muddled and blotchy. I’ll attempt to fix it up a bit by burnishing some areas lighter– including her mustache. I may also work back into the new backdrops with some line work to unify the images.
The way it works: the spit (or, if you’re squeamish, gum arabic) breaks the surface tension, allowing the acid to move around the plate freely, within the areas you apply it with a brush. It also dilutes the acid, so you can have it different strengths in different areas. The key is to allow the acid to meander, slowly– you tip and tilt the plate so no hard edges result. Diluting with water and periodic rinsing to “stop” the action are also possibilities. How dark your tonalities get is about how long the solution rests in any given area. It reminded me of nothing so much as when I worked on photo prints in a darkroom, applying similarly loose time-based approaches with the developing solution– not just sitting in the bath, but pouring it over some areas more than others. It’s a watercolor-esque approach to biting the surface of your copper plate.
(Looking at it in this way, one might wonder why photography took so many centuries after the printmaking process was developed. But then, reining in light is a far different prospect than reining in metal…)