Spit-Biting and Photopolymer

Or, how I learned to rethink my materials, again.

This post follows on the heels of the last (“Blocking Light In a Creative Way”), and recounts another scenario where I made a major inroad in how I approach media, process, and critical thinking.

One of the major themes in my studio practice is adaptation. Besides narrowing down what makes something unique, I really love thinking about how to make a particular idea work when you’re lacking crucial components of a traditional process. (There’s that mother of invention thing again…)

In my explorations of working photopolymer directly, I wondered how I could affect the surface further without the use of transparencies. Going down the list of processes used on metal plate, I thought spit-biting might be one of most adaptable.

Knowing the photopolymer plate is water soluble,  a water-based wash could/would “etch” the plate, but how could I control it? In traditional spit-biting, an acid wash is used to etch the metal, and water is used to dilute the strength of the wash. But how do I “water-down” the etching strength of water?

In the manufacturer’s material safety data sheet (MSDS) for the plate there is a section which lists the plate’s physical and chemical properties. This list indicated that the polymer is not only soluble in water, but also in alcohol. With a couple of tests, I was able to determine that water was the stronger enchant and that alcohol had only a mild affect on the plate. Side note: in this case, when I say ” alcohol” I am referring to isopropyl alcohol. I did test denatured, as well as vodka, but ethanol didn’t appear to work as well as isopropyl. This was an advantageous detail, since isopropyl is sold in a variety of strengths in the drugstore as rubbing alcohol (70% to 90%), and then can be found in lab-grade strength (called propanol) through science supplies stores. Obviously, the strength can be adjusted by merely mixing different ratios of water to alcohol, but it’s nice to have pre-mixed sources for consistency.

The Method

I kept my experiments pretty loose just to see how the water would even affect the surface of the plate. I went for random washes, without any attempt at achieving a likeness.

With regards to timing of etches, I sort of combined the approach of traditional spit biting with that of washes in lithography, where the solution was allowed to etch the surface, but was also left to dry to see how the surface might change with gradual evaporation. A touche wash on a litho stone will leave a reticulation of pigment, what might a slowly drying puddle of etchant leave? The photos below show some of the results. One of the most interesting things is how the alcohol acts almost like rain on a dry desert floor; it penetrates, and then dries in a way that the surface fractures. The water plays differently on the surface as the deeper saturation and longer drying time allows for a softer and rounder reticulation.

Once the plate is mostly dry from the etches, I heat treat it with a blow dryer, and then place the plate under the exposure unit (sans vacuum). Once exposed, the process remains the same: the plate still needs to have its protective layer washed away in the developer bath, it still needs a heat treat, and the curing exposure. The plate, at this point, is sort of a combination of an etching and a collograph.

These experiments were done in 2013.

More on how pigment and aquatint can be added to the mix next time…


The content presented here is a documentation of my own experiments. While I can account for my own actions and safety, I cannot account for yours. IF you decide to attempt or tinker with similar experiments to my own, PLEASE focus your utmost attention to safety and critical thinking. I am not responsible, in any way, for misunderstandings or mishaps resulting in material or physical harm. Proceed at your own risk.

test of water wash on blank photoploymer plate.
isopropyl alcohol puddle test on blank photopolymer plate.
isopropyl alcohol puddle test on blank photopolymer plate.
water and alcohol test on blank plate.

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