Etching is a printmaking process dating back to the 15th century, using metal plates and pressure to make images. Albrecht Durer, Rembrandt, Goya, William Blake and Picasso all made etchings, as well as countless other artists through the centuries.
Basic etching involves six key elements: A metal plate, an acid bath or other corrosive substance, an acid resist, ink, paper, and pressure.
First, the metal plate. The plate must be prepared, which involves cleaning and polishing the surface of the plate and filing the edges of the plate to a bevel. This is done so that the edges of the plate don't cut through the paper when it's being printed.
Next, the plate is cleaned, and when it is free from all oils and dirt, an acid resist is applied. This can be any number of things, but for the purpose of this explanation, we'll say it's hard ground. Hard ground is a liquid varnish of sorts that is simply painted on the metal plate and left to dry.
Once the plate is covered with hard ground and dried, the artist uses a small sharp tool to draw a design or image onto the metal plate. Here you can see that where the drawing is, the metal plate is exposed.
Once you have a drawing on your plate, it's time to put it in the acid bath. The metal plates I use are zinc, and they dissolve in nitric acid. The acid is very dilute (a 35% solution diluted at a ratio of 1:10), so the zinc dissolves slowly. Once you place the plate into the acid bath, the tiny exposed parts of the plate begin to dissolve, leaving behind etched lines.
When the acid has dissolved the right amount of zinc, the plate comes out of the acid bath and gets rinsed off and cleaned. At this point, the work is assessed and either the process is repeated to make more lines on the plate, or it's time to print!
Printing is started by inking the plate. Ink is applied using a small card, and the ink is scraped across the plate surface. It's important not to get too much ink on the plate, but there must be enough ink to work down into every one of the tiny etched lines.
Next, the excess ink is wiped off the plate using a piece of tarlatan, a material similar to cheesecloth.
After this, the surface of the plate is polished clean with a scrap of newsprint or newspaper.
Edges are cleaned to ensure a good print.
After that, the plate is ready to print. The plate is placed face up on the press bed, covered with clean, damp paper, and then covered with a sheet of newsprint. The press blankets are lowered over all of that, and the print is ready to run!
On its trip through the press, the plate and paper will be subjected to an incredible amount of pressure. Enough pressure to squish the paper into every teeny tiny little crevice of the plate. The paper gets pressed down into each crevice, and picks up the ink, and that's how an etching is made!
Etching is a complicated process and there are many different techniques that can be used, but this is a brief explanation of the most basic technique. Whew!