Intaglio and the Etching Process

Etching is an intaglio printmaking process: the image is held in incised lines and recesses below the plate surface, and ink is wiped into those incisions. A dampened sheet of paper is then pressed against the plate under high pressure, pulling the ink from the grooves onto the paper. Unlike relief printing, it is the cut areas that transfer ink, not the surface.

The etching process uses acid to cut into the metal. The artist draws through an acid-resistant coating (the ground), exposing the metal beneath, then places the plate in an acid bath. Where the ground is removed, acid bites into the metal, creating the recessed lines that will hold ink.

Plate Material: Zinc vs. Copper

Zinc is the most commonly used plate material for studio etching in Poland, partly because of cost and partly because it is more responsive to many acid types. Zinc reacts readily with nitric acid and ferric chloride, biting quickly and producing slightly rougher line edges compared with copper. This can be an advantage for expressive line work and a disadvantage where precise fine line control is needed.

Copper bites more slowly and evenly in ferric chloride, which is the preferred acid for copper. The resulting lines are cleaner and hold finer detail. Copper plates also withstand longer print editions before the incised lines show wear. The higher cost of copper plate is a factor in studio choice.

Acid safety note: All acid work must be carried out in a ventilated space. Nitric acid produces toxic fumes; ferric chloride is a safer alternative for studio use and is preferred in many European printmaking workshops. Always use appropriate acid-resistant gloves and eye protection.

Preparing the Plate

Step 1

Degreasing

The plate surface must be completely free of oil, fingerprints, and oxidation before ground is applied. Scrub the surface with a slurry of whiting powder (calcium carbonate) and water using a damp rag, working in small circular motions. Rinse thoroughly and dry with clean paper, touching only the edges of the plate thereafter. The degreased surface should sheet water evenly — any beading indicates remaining grease.

Step 2

Applying Hard Ground

Hard ground is a wax-resin mixture that sets firm when cooled on the plate. Place the plate on a hotplate at approximately 60–70 °C. Roll the hard ground ball across the heated surface — it melts and spreads. Use a brayer to roll the melted ground into a thin, even layer across the plate. The ground should appear dark brown to black when even. Allow the plate to cool completely before drawing into it. Uneven ground coverage (thin patches or pinholes) will result in unintended bite marks during acid exposure.

Drawing Through the Ground

Step 3

Etching Needle Selection

A blunt or rounded needle point is preferable for most etching work. A sharp pointed needle removes ground cleanly but may skate and produce variable line widths; a slightly rounded point gives more consistent control and a slightly wider initial bite. The needle should scratch through the ground to expose the bare metal without cutting into the metal itself at this stage — the acid does the cutting, not the needle.

Step 4

Drawing Technique

Work on a light table or under a lamp to see the ground clearly. Draw through the ground as you would draw with a pen on paper. Lines left as bare metal will be bitten by acid; areas still covered by ground will print as whites. For tonal areas, use closely spaced parallel lines or cross-hatching — the acid does not produce tonal gradients automatically, as in drypoint or aquatint.

Acid Biting

Step 5

Preparing the Acid Bath

Ferric chloride solution (40–45 Baumé concentration, or approximately 43% by weight) is the most widely recommended acid for both zinc and copper in current European studio practice. It does not produce toxic fumes at normal working concentrations and can be disposed of through specialist chemical waste collection. Keep the solution in a covered, acid-resistant tray (polypropylene or ceramic). Do not use metal containers.

Step 6

Biting the Plate

Lower the plate into the ferric chloride tray with the drawing face down (face-down biting prevents sediment from collecting in the bitten lines and blocking acid access). Agitate the tray gently at intervals, or use a circulation pump. Check biting progress by removing the plate, rinsing briefly, and inspecting with a loupe. Biting times vary significantly with acid freshness and temperature. Initial fine lines may require as little as 5 minutes; broader tonal areas may require 20–40 minutes of cumulative biting.

Step 7

Stop-Out and Staged Biting

For plates with lines of different intended depths (and therefore different tonal weight in printing), stop-out varnish is applied to lines that have reached the desired depth before returning the plate to the acid. This allows progressively deeper biting of remaining lines. Plan the tonal hierarchy of the image before biting begins, working from lightest (shortest acid exposure) to darkest (longest).

Cleaning and Finishing the Plate

Step 8

Removing the Ground

After biting is complete, remove the plate from the acid bath and rinse with water. Dissolve the hard ground with mineral spirits (white spirit) applied with a rag. The ground lifts completely, leaving the bare metal surface with the bitten lines visible as shallow grooves. Inspect the plate in raking light to assess the depth and character of the lines before proceeding to printing.

Printing the Etched Plate

Step 9

Inking the Plate

Use etching ink, which is stiffer than relief ink and formulated to wipe cleanly from the plate surface while remaining in the incised lines. Apply ink with a stiff card or tarlatan dauber, working it into the lines from multiple directions. Then wipe the surface with clean tarlatan, using light circular motions to remove surface ink without pulling ink from the grooves. The final wipe is done with the palm of the hand to produce a plate tone, or with a clean page of telephone directory paper for a whiter ground. Wipe from the centre of the plate outward to avoid smearing ink from the edges onto the printing surface.

Step 10

Printing on the Press

Place the inked plate on the bed of the etching press. Position dampened printing paper over the plate (dampen paper by misting and stacking between damp newsprint blotters for several hours; paper should be limp but not wet). Cover with press blankets and run through the press at sufficient pressure to force paper into the bitten lines. Typical etching press pressure is set to leave a clear plate mark (embossed edge of the plate visible in the paper). Peel the print back carefully and hang to dry flat.

Aquatint: Adding Tone

Aquatint is a variant of etching that produces tonal areas rather than lines. A fine resin or spray lacquer is deposited on the plate; when bitten in acid, the metal bites around each resin particle, creating a porous surface that holds a thin layer of ink and prints as a flat tone. Longer biting produces darker tones. Aquatint is often combined with line etching on the same plate.

References

  • Chamberlain, Walter. The Thames and Hudson Manual of Etching and Engraving. Thames and Hudson, 1972.
  • Wikipedia contributors. Etching. Wikipedia, The Free Encyclopedia.
  • Printmaking Today. printmakingtoday.co.uk.