Process talk: Aluminum etching

Palmystery – Photo-litho etching and relief monoprint; variable edition, 2022; Akua intaglio on Rives BFK; 12″x12″

Many people have used the term “etching” as a joke, as in “come up to my place to see my etchings.” We all know what that means, but most people may not know what etching means to printmaking.

Etching is an intaglio process — a design inscribed into a surface, or “plate”, ink is applied to the incisions and transferred to paper. It’s a technical process involving acid that bites into the raw metal to create the incisions. Acid-activated etching is done on metal. Drypoint is another intaglio process that doesn’t require acid, and which can be done on plastic, metal or even milk cartons.

This year I’ve been learning acid-based etching. I started with a relatively safe process involving copper-sulfate acid on aluminum, and fell in love with the grungy effects I can get.

Here’s how it works:

  • I start with a photo or scanned drawing and create a high-contrast image in photo-editing software. That image is converted to negative and printed to a polyester lithography plate (aka “Pronto plate”) via my laser printer.
  • Next, I transfer the image to an aluminum plate to create a resist for the acid bath. This resist is called a “ground”, which protects the areas that will not be etched in the acid bath. Here’s how:
    1. I transfer the laser-printed image using a lithography process in which Baldwin Intaglio Ground (or “BIG”, a non-toxic substance) is used instead of oil ink.
    2. I then place the inked pronto plate on a clean, degreased aluminum plate and run it through my etching press, Patsy.
    3. The ink is hardened in my homemade “oven” consisting of a cardboard box and a blow-dryer for about 25 minutes.
  • Once the ink — or ground — is thus transferred to the aluminum, the aluminum plate is placed in a relatively low-toxicity copper-sulfate bath for about 16 minutes. I love to watch the bits burble up from that lovely flat, shiny piece of metal:
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