What is Etching?
Etching is traditionally the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio (incised) in the metal. As a method of printmaking, it is, along with engraving, the most important technique for old master prints. It was used by Rembrandt with differential inking to get very varied chiaroscuro effects.
Bibliography of sources consulted
- Bikker, J. & Weber, G. J. M., (2015) Rembrandt: The Late Works, London, National Gallery.
- Cohen, J. (ed.) (1995) Picasso: Inside the Image, London: Thames & Hudson.
- Coppel, S., (1998) Picasso and Printmaking in Paris, London, South BGank Publishing.
- Grabowski, B. & Flick, B., (2009) Printmaking: A Complete Guide to Materials and processes, London, Lawrence King Publishing.
- Hambling, M., (2009) The Sea, Salford Quays, The Lowry Press.
- Pogue, D., (2012) Printmaking Revolution : new advancements in technology, safety and sustainability, New York, watson-guptill publications.
- Royalton-Kisch, M., (2006) Rembrandt as Printmaker, London, Hayward Gallery Touring.
- David Borrington notes from Curwen Studio
- Own practical notes and experiments
1) Preparing the plate: different types of etching
Etching is done on metal plates that differ both in durability and ease/speed of etching. The type of metal used for the plate impacts the number of prints the plate will produce. The firm pressure of the printing press slowly rubs out the finer details of the image with every pass-through.
- Copper is a traditional metal, and is still preferred, for etching, as it bites evenly, holds texture well, and does not distort the color of the ink when wiped. It can produce a few hundred printings of a strongly etched imaged before the degradation is considered too great by the artist. At that point, the artist can manually restore the plate by re-etching it, essentially putting ground back on and retracing their lines; alternatively, plates can be electro-plated before printing with a harder metal to preserve the surface.
- Zinc is cheaper. As a softer metal, etching times are shorter, but it does not bite as cleanly as copper does, and it alters some colours of ink. Softness also leads to faster degradation of the image in the press.
- Steel is growing in popularity as an etching substrate. Increases in the prices of copper and zinc have steered steel to an acceptable alternative. The line quality of steel is less fine than copper, but finer than zinc. Steel has a natural and rich aquatint.
The plate needs first to be cleaned to be clear from marks and finger prints. With Whiting.
The plate is then covered with a waxy ground that is resistant to acid. The nature of the ground affects the type of line, possibilities for tonal additions and inking. There are a number of distinct methods.
- Hard ground
This gives a sharp and defined line with tone achieved either through different types of cross-hatching and/or differential wiping of the plate.
Hard ground can be applied in two ways.
Solid hard ground comes in a hard waxy block. To apply hard ground of this variety, the plate to be etched is placed upon a hot-plate (set at 70 degrees C), a kind of metal worktop that is heated up. The plate heats up and the ground is applied by hand, melting onto the plate as it is applied. The ground is spread over the plate as evenly as possible using a roller. Once applied the etching plate is removed from the hot-plate and allowed to cool which hardens the ground.
Liquid hard ground comes in a can and is applied with a brush upon the plate to be etched. Exposed to air the hard ground will harden. Some printmakers use oil/tar based as hard ground, although often bitumen is used to protect steel plates from rust and copper plates from ageing.
The design is then drawn (in reverse) with an etching-needle or échoppe where want a line to appear in the finished piece, so exposing the bare metal. The échoppe, a tool with a slanted oval section, is also used for “swelling” lines. An “echoppe” point can be made from an ordinary tempered steel etching needle, by grinding the point back on a carborundum stone, at a 45–60 degree angle. The “echoppe” works on the same principle that makes a fountain pen’s line more attractive than a ballpoint’s: The slight swelling variation caused by the natural movement of the hand “warms up” the line, and although hardly noticeable in any individual line, has a very attractive overall effect on the finished plate. It can be drawn with in the same way as an ordinary needle.
The work on the plate can also be added to by repeating the whole process; this creates an etching which exists in more than one state.
Gives a softer line with more variation in thickness, where tone can also be achieved through cross-hatching and shading as in ink drawing, and differential inking.
This uses a special softer ground. The artist places a piece of paper (or cloth etc. in modern uses) over the ground and draws on it. The print resembles a drawing.
Soft ground also comes in liquid form and is allowed to dry but it does not dry hard like hard ground and is impressionable. After the soft ground has dried the printmaker may apply materials such as leaves, objects, hand prints and so on which will penetrate the soft ground and expose the plate underneath.
After the ground has hardened the artist “smokes” the plate, classically with 3 beeswax tapers, applying the flame to the plate to darken the ground and make it easier to see what parts of the plate are exposed. Smoking not only darkens the plate but adds a small amount of wax. Afterwards the artist uses a sharp tool to scratch into the ground, exposing the metal.
Aquatint uses acid-resistant resin to achieve tonal effects.
Particulate resin is evenly distributed on the plate using a special box. Resin is hazardous to health and it is important not to inhale.
The plate is then heated to form a screen ground of uniform, but less than perfect, density.
After etching, any exposed surface will result in a roughened (i.e., darkened) surface. Areas that are to be light in the final print are protected by varnishing between acid baths. Successive turns of varnishing and placing the plate in acid create areas of tone difficult or impossible to achieve by drawing through a wax ground.
This gives a more painterly line.
Designs in a syrupy solution of sugar or Camp Coffee are painted onto the metal surface prior to it being coated in a liquid etching ground or ‘stop out’ varnish. When later the plate is placed in hot water the sugar dissolves and lifts off leaving the image. The plate can then be etched.
Relief etching was invented by William Blake in about 1788, and he has been almost the only artist to use it in its original form. However, from 1880–1950 a photo-mechanical (“line-block”) variant was the dominant form of commercial printing for images. A similar process to etching, but printed as a relief print, so it is the “white” background areas which are exposed to the acid, and the areas to print “black” which are covered with ground. Blake’s exact technique remains controversial. He used the technique to print texts and images together, writing the text and drawing lines with an acid-resistant medium.
Invented in 2006 and yields an image like that of a charcoal drawing:
2) Etching the plate
The plate is then completely submerged in a bath of acid technically called the mordant (French for “biting”) or etchant, or has acid washed over it. Ferric chloride may be used for etching copper or zinc plates, whereas nitric acid may be used for etching zinc or steel plates.
- The acid “bites” into the metal (it dissolves part of the metal) where it is exposed, leaving behind lines sunk into the plate. The waxy resist prevents the acid from biting the parts of the plate which have been covered.
- The strength of the acid determines the speed of the etching process. Typical solutions are 1 part FeCl3 to 1 part water and 1 part nitric to 3 parts water.
- The longer the plate remains in the acid the deeper the “bites” become.
During the etching process the printmaker uses a bird feather or similar item to wave away bubbles and detritus produced by the dissolving process, from the surface of the plate, or the plate may be periodically lifted from the acid bath. If a bubble is allowed to remain on the plate then it will stop the acid biting into the plate where the bubble touches it. Zinc produces more bubbles much more rapidly than copper and steel and some artists use this to produce interesting round bubble-like circles within their prints for a Milky Way effect.
The detritus is powdery dissolved metal that fills the etched grooves and can also block the acid from biting evenly into the exposed plate surfaces. Another way to remove detritus from a plate is to place the plate to be etched face down within the acid upon plasticine balls or marbles, although the drawback of this technique is the exposure to bubbles and the inability to remove them readily.
For aquatinting a printmaker will often use a test strip of metal about a centimetre to three centimetres wide. The strip will be dipped into the acid for a specific number of minutes or seconds. The metal strip will then be removed and the acid washed off with water. Part of the strip will be covered in ground and then the strip is redipped into the acid and the process repeated. The ground will then be removed from the strip and the strip inked up and printed. This will show the printmaker the different degrees or depths of the etch, and therefore the strength of the ink color, based upon how long the plate is left in the acid.
A mixture of nitric acid and/or gum arabic and/or rosin and/or water (or almost never – saliva) is applied to certain areas of the plate with a brush, dripped, spattered or painted onto a metal surface giving interesting results. The plate may be aquatinted for this purpose or exposed directly to the acid.
3) Cleaning the plate
The plate is removed from the acid and washed over with water to remove the acid. The remaining ground is removed with a solvent such as turpentine. Turpentine is often removed from the plate using methylated spirits since turpentine is greasy and can affect the application of ink and the printing of the plate.
Foul-bite or “over-biting” is common in etching, and is the effect of minuscule amounts of acid leaking through the ground to create minor pitting and burning on the surface. This incidental roughening may be removed by smoothing and polishing the surface, but artists often leave faux-bite, or deliberately court it by handling the plate roughly, because it is viewed as a desirable mark of the process.
The remaining ground is then cleaned off the plate. The plate is inked all over, and then the ink wiped off the surface, leaving only the ink in the etched lines.
A piece of matte board, a plastic “card”, or a wad of cloth is often used to push the ink into the incised lines.
- Oil based etching inks
- Akua inks – don’t find these too good.
The surface is wiped clean with a piece of stiff fabric known as tarlatan and then wiped with newsprint paper; some printmakers prefer to use the blade part of their hand or palm at the base of their thumb. You may also use a folded piece of organza silk to do the final wipe.
If copper or zinc plates are used, then the plate surface is left very clean and therefore white in the print. If steel plate is used, then the plate’s natural tooth gives the print a grey background similar to the effects of aquatinting. As a result, steel plates do not need aquatinting as gradual exposure of the plate via successive dips into acid will produce the same result.
Differential inking can significantly affect the impact of the image – as exploited by eg Rembrandt and can be seen on the markmaking on the etching plate in the prints below.
The plate is then put through a high-pressure printing press together with a sheet of paper (often moistened to soften it).
The paper picks up the ink from the etched lines, making a print. The process can be repeated many times; typically several hundred impressions (copies) could be printed before the plate shows much sign of wear.
Printing the plate is done by covering the surface with printing ink, then rubbing the ink off the surface with tarlatan cloth or newsprint, leaving ink in the roughened areas and lines. Damp paper is placed on the plate, and both are run through a printing press; the pressure forces the paper into contact with the ink, transferring the image (c.f., chine-collé).
Growing concerns about the health effects of acids and solvents led to the development of less toxic etching methods in the late 20th century. An early innovation was the use of floor wax as a hard ground for coating the plate. Others, such as printmakers Mark Zaffron and Keith Howard, developed systems using acrylic polymers as a ground and ferric chloride for etching. The polymers are removed with sodium carbonate (washing soda) solution, rather than solvents. When used for etching, ferric chloride does not produce a corrosive gas, as acids do, thus eliminating another danger of traditional etching.
The traditional aquatint, which uses either powdered rosin or enamel spray paint, is replaced with an airbrush application of the acrylic polymer hard ground. Again, no solvents are needed beyond the soda ash solution, though a ventilation hood is needed due to acrylic particulates from the air brush spray.
The traditional soft ground, requiring solvents for removal from the plate, is replaced with water-based relief printing ink. The ink receives impressions like traditional soft ground, resists the ferric chloride etchant, yet can be cleaned up with warm water and either soda ash solution or ammonia.
Anodic etching has been used in industrial processes for over a century. The etching power is a source of direct current. The item to be etched (anode) is connected to its positive pole. A receiver plate (cathode) is connected to its negative pole. Both, spaced slightly apart, are immersed in a suitable aqueous solution of a suitable electrolyte. The current pushes the metal out from the anode into solution and deposits it as metal on the cathode. Shortly before 1990, two groups working independently developed different ways of applying it to creating intaglio printing plates.
In the patented Electroetch system, invented by Marion and Omri Behr, in contrast to certain nontoxic etching methods, an etched plate can be reworked as often as the artist desires.The system uses voltages below 2 volts which exposes the uneven metal crystals in the etched areas resulting in superior ink retention and printed image appearance of quality equivalent to traditional acid methods. With polarity reversed the low voltage provides a simpler method of making mezzotint plates as well as the “steel facing”copper plates.
Some of the earliest printmaking workshops experimenting with, developing and promoting nontoxic techniques include Grafisk Eksperimentarium, in Copenhagen, Denmark, Edinburgh Printmakers, in Scotland, and New Grounds Print Workshop, in Albuquerque, New Mexico.
Light sensitive polymer plates allow for photorealistic etchings. A photo-sensitive coating is applied to the plate by either the plate supplier or the artist. Light is projected onto the plate as a negative image to expose it. Photopolymer plates are either washed in hot water or under other chemicals according to the plate manufacturers’ instructions. Areas of the photo-etch image may be stopped-out before etching to exclude them from the final image on the plate, or removed or lightened by scraping and burnishing once the plate has been etched. Once the photo-etching process is complete, the plate can be worked further as a normal intaglio plate, using drypoint, further etching, engraving, etc. The final result is an intaglio plate which is printed like any other.
You Tube Tutorials