Process: Intaglio: Etching: Acid Zinc Plate
- Design: Create a precise rendering the same scale as the print. 6”x9” plate
- Select metal: Zinc is a good student grade; copper is used as a studio grade.
- [If you are using the commercial ground on your plate skip to 9]
- Degrease plate: Clean metal of oil film with ammonia water or commercial metal cleaner. If water continues to bead the metal needs further cleaning. Water should sheet off the plate. Avoid touching plate with fingers.
- Warm up plate: (optional) Place the plate onto a hot plate and get it warm. Minimum of one minute on low temperature.
- Coat plate with ground: (acid-resistant substance). Hard grounds hold fine linear work without chipping or flaking from the surface. The plate should be sitting diagonally. With a soft brush apply liquid hard ground across the plate, beginning at the top. Think of applying wash to a watercolor. A brayer may be used. The ground (asphaltum) should appear brown (if it appears black it is too thick, and tan will not withhold multiple runs). False biting takes place if pinholes appear on the plate.
- Warm up again: (optional) heating the plate after the liquid hard ground has been applied will help soften and even out the coating. Allow cooling before printing.
- Smoke the plate: (optional) to make the ground darker so the exposed metal is more visible you may smoke the ground. Let the flame not the wick dance on the surface of the ground. As the carbon mixes with the ground, it hardens slightly.
- Transfer drawing: You may use a projector. White chalk on the back of your sketch on tracing paper works well for transfer. You may run it through the press or burnish with a wooden spoon. Black or white carbon paper can be used face-down and traced from the back with a pencil. Red conté or white chalk on a thin paper also works well.
- Draw with needle: Draw on the ground with an etching needle (well rounded and not too sharp) exposing the metal. Stippling and hatching with needle and various mezzotint tools create variations of tone. Use light but sufficient pressure. A pencil may be used (6H). Open Bite: Remove larger areas with a q-tip and turpentine.
- Block out the sides and the back with ground.
- The Acid Bath: Fumes from most acids are dangerous. Flush with water if an accident occurs. When mixing always pour the acid into the water. Wear polyurethane gloves. An acid bath can be used several times for the same type of metal, but separate baths must be made for each metal. Nitric acid turns brilliant blue-green after etching copper or brass, and a cloudy gray after etching zinc. The mordants most commonly used for etching copper, zinc, steel, and other metal plates are ferric chloride (most safe), nitric acid and the Dutch mordant. If using the ferric chloride bath face the plate upside down on small pieces of wood about ¼ from the bottom allowing the iron oxide to fall to the bottom of the bath. The nitric acid is mixed at 1/5th ratio with water. Use a Baumé hydrometer to find the solution strength. In saturated form it comes in 45 degrees Baumé. Adding water reduces the density of the fluid. Dry crystals are also available.
- Lower plate into bath: The plate should be lowered into the acid bath with a stick or a piece of polyester string. At the very least, do not drop; rather lay gently the plate in the bath (splashing issue).The plate is placed into the acid bath, so the drawn areas are exposed by the needle are etched out. The length of time in the acid and the strength of the solution determine both the width and the depth of the line.
- A line bitten slowly in a weak acid will be much sharper than one bitten for a short time in strong acid.
- Wipe away bubbles with a feather during the bite.
- Examine the plate during printing to check the depth of bite. The plate may occasionally have to be dipped into a 20% acetic acid bath to remove any residue.
- (optional) Use stopping out method by applying stop-out varnish or liquid ground. The lightest lines are stopped out after a brief time in the etching bath. Then, in successive stages, the other lines are covered until the stopping out is completed. Use a good brush with a fine point
- Remove plate and rinse under water faucet.
- Clean off ground: The remaining ground is removed with solvent and the plate prepared for printing. [Oil based clean procedure.]
- Polish plate with a charcoal block, jeweler’s rouge or liquid metal polish and a soft cloth (crocus cloth) to ensure an even printing of surface.
- Bevel edges: File the rough and sharp edges after the acid bath. Steel wool removes file marks from edge of plate. Sharp edges will cut your print.
- Fill in ink with dauber (rolled felt) and scrape off extra with a piece of cardboard. Use tissue to finish wiping. Remember to wipe the edges. Clean hands!
- The paper must dampen without falling apart and must pick up the finest detail on the plate. Rag papers-either handmade or mold made-are traditional for intaglio printing. They have longer fibers than the cheaper wood-pulp papers, as well as low sizing content. Good-quality paper is made of recycled or new cotton fibers. Select from the following: American Etching, Arches-Test or Cover Stock, Copper Plate Deluxe, German Etching, Italia, Lenox 100, Murillo, Rives-Lightweight, Heavyweight, BFK (cover), Strathmore Etching, J. Barcham Green.
- Ink: Good ink is buttery, heavily pigmented, and neither too coarsely nor too finely ground. Graphic Chemical and Ink Company makes good ink.
- Ink is applied with a roller, a dauber or a card made from mat board. Push the ink into all the lines and crevices of the plate. A roller works well. Avoid excessive rubbing and pressure.
- Get three or four pads of tarlatan ready. Wash the starch out of the tarlatan first. Consider plate tone as you wipe. You may use newsprint or pages from an old telephone book.
- Clean hands.
- Dampen paper with sponger or dip in water bath and use blotter paper. Heavyweight paper will need considerable more water than a thinner one. Place paper in water and place under weight.
- Print: After making sure that the edges of the plate have been wiped clean,
- Lay paper towels on press. Put inked plate face up on towels. Newspaper will leave image.
- Use some paper tabs to pick up the damp printing paper, and place it on the plate. Lay damp paper on top of inked plate.
- Use a sheet of registration paper under the plate (if print is large, or if using multiple plates). Only run a print through the press one time.
- Allow print to dry for a few days on drying rack. Print must never stay on drying rack more then one week.
- Add Dry Point and/or Engraving afterwards.
- Flatten paper under weight for a day.
Note: Water/Etch® Acidless Plates are an acid free option. They are light sensitive plastic coated plates with a steel backing.
The photopolymer emulsion is biodegradable and can be etched with light.
Other Project: Etching copper. Use PCB etching solution (from Radio Shack). Sharpie marker, fingernail polish.