Editing Etching (section)

==Printmaking technique in detail==
[[File:Tools of etching.svg|thumb|600px|left|Steps in the typical technique]]
A waxy acid-resist, known as a ground, is applied to a metal plate, most often [[copper]] or [[zinc]] but [[steel]] plate is another medium with different qualities. There are two common types of ground: hard ground and soft ground.

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&nbsp;°C, 158&nbsp;°F), 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.

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.
[[File:America a Prophecy copy a plate 01.jpg|thumb|Relief etching by William Blake, frontispiece to ''[[America a Prophecy]]'' (Copy A, printed 1795)]]
[[Image:Paula Modersohn-Becker Landschaft unter Bäumen.jpg|thumb|right|''Landscape under Trees'', etching by [[Paula Modersohn-Becker]], c.&nbsp;1902]]

The second way to apply hard ground is by liquid hard ground. This 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 [[asphaltum]]<ref>{{cite web|url=http://www.magical-secrets.com/studio/glossary |title=Glossary &#124; Magical-Secrets: A Printmaking Community |publisher=Magical-Secrets |access-date=2015-08-11}}</ref> or [[bitumen]] as hard ground, although often bitumen is used to protect steel plates from rust and copper plates from aging.

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.

The ground can also be applied in a fine mist, using powdered rosin or spraypaint. This process is called aquatint, and allows for the creation of tones, shadows, and solid areas of color.

The design is then drawn (in reverse) with an etching-needle or échoppe. 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 plate is then completely submerged in a solution that eats away at the exposed metal. [[Iron(III) chloride|ferric chloride]] may be used for etching copper or zinc plates, whereas [[nitric acid]] may be used for etching zinc or steel plates. Typical solutions are 1 part FeCl<sub>3</sub> to 1 part water and 1 part nitric to 3 parts water. The strength of the acid determines the speed of the etching process.
* The etching process is known as ''biting'' (see also spit-biting below).
* The waxy resist prevents the [[acid]] from biting the parts of the plate which have been covered.
* The longer the plate remains in the acid the deeper the "bites" become.

[[Image:Aetzung Landschaft.jpg|thumb|left|Example of etching]]
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.

The plate is removed from the acid and washed over with water to remove the acid. The 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.

Spit-biting is a process whereby the printmaker will apply acid to a plate with a brush in certain areas of the plate. The plate may be aquatinted for this purpose or exposed directly to the acid. The process is known as "spit"-biting due to the use of saliva once used as a medium to dilute the acid, although gum arabic or water are now commonly used.

[[Image:Félicien Rops - Pornokratès - 1878 (2).jpg|thumb|''Pornocrates'' by [[Félicien Rops]]. Etching and [[aquatint]]]]
A piece of matte board, a plastic "card", or a wad of cloth is often used to push the ink into the incised lines. 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. The wiping leaves ink in the incisions. 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.
[[File:Allan Osterlind Flamencotänzerin.jpg|thumb|Colored etching and aquatint on paper]]
A damp piece of paper is placed over the plate and it is run through the press.

===Nontoxic etching===
{{History of printing}}
Growing concerns about the health effects of acids and solvents<ref>{{cite web |url=http://web.princeton.edu/sites/ehs/artsafety/sec13.htm |title=Welcome to the Office of Environmental Health and Safety &#124; Office of Environmental Health and Safety |publisher=Web.princeton.edu |access-date=2015-08-11 |archive-url= https://web.archive.org/web/20120826014445/http://web.princeton.edu/sites/ehs/artsafety/sec13.htm |archive-date=2012-08-26 |url-status=dead }}</ref><ref>{{cite web|url = http://www.chicagoartistsresource.org/node/9287|title = Intaglio Health and Safety: Overview|first1 = Angela|last1= Babin|first2= Michael|last2= McCann |archive-url= https://web.archive.org/web/20120825165930/http://www.chicagoartistsresource.org/node/9287 |archive-date=August 25, 2012 |website = Chicago Artists Resource}}</ref> led to the development of less toxic etching methods<ref>{{cite web|url=http://www.greenart.info/galvetch/etchtabl.htm |title=Traditional intaglio printmaking methods, their health hazards, new non-toxic substitutes |publisher=Greenart.info |date=2013-03-14 |access-date=2015-08-11}}</ref> 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 polymer]]s 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<ref>{{Citation | last1 = Behr | first1 = Marion | last2 = Behr | first2 = Omri | title = Environmentally safe Etching | journal = Chemtech | volume = 21 | issue = 4 | pages = 210 | year = 1991}}</ref><ref>{{cite journal|last1=Nick|first1=Semenoff|last2=Christof|first2=C.|title=Using Dry Copier Toners in Intaglio and Electro-Etching of metal Plates|journal=Leonardo|date=1999|volume=24|issue=4|pages=389–394|doi=10.2307/1575513|publisher=MIT Press|jstor=1575513|s2cid=191386942}}</ref> developed different ways of applying it to creating intaglio printing plates.

In the patented<ref>{{cite patent | inventor1-last = Behr | inventor1-first = Marion | inventor2-last = Behr | inventor2-first = Omri | fdate = 11990-10-31 | pubdate = 1992-04-07 | title =Electrolytic etching process and apparatus therefor | country= US | number = 5102520 }}. The voltage should be adjustable to operate accurately within a rather narrow voltage range, such that the minimum voltage shall be at least that of the ionization potential of the metal object in the electrolyte chosen and the maximum shall not substantially exceed the sum of the decomposition voltage of the aqueous electrolyte and the over-voltage of the cathode selected.</ref><ref>{{cite patent | inventor1-last = Behr | inventor1-first = Omri | inventor2-last = Behr | inventor2-first = Marion | fdate = 1992-11-05 | pubdate = 1992-05-12 | title = Method and apparatus for producing etched plates for graphic printing | country= US | number =5112453}}</ref> 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<ref>{{Citation | last1 = Behr | first1 = Marion | last2 = Behr | first2 = Omri | title = Etching and Tone Creation Using Low-Voltage Anodic Electrolysis | journal = Leonardo | volume = 26 | issue = #1 | pages = 53– | year = 1993 | doi=10.2307/1575781| jstor = 1575781 | s2cid = 100716855 }}</ref><ref>{{Citation | last = Behr | first = Marion | title = Electroetch, a safe etching system | journal = Printmaking Today | volume = 3 | issue = #1 | pages = 18– | year = 1993 }}</ref><ref>{{Citation | last = Behr | first = Marion | title = Electroetch II | journal = Printmaking Today | volume = 4 | issue = #4 | pages = 24– | year = 1995}}</ref><ref>{{Citation | last1 = Behr | first1 = Marion | last2 = Behr | first2 = Omri | title = Setting the record straight | journal = Printmaking Today | volume = 7 | issue = 4 | pages = 31–32 | year = 1998 }}</ref> 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"<ref>{{Citation | last = Behr | first = Omri | title = An improved method for steelfacing copper etching plates | journal = Leonardo | volume = 30 | issue = #1 | pages = 47–48 | year = 1997| doi = 10.2307/1576375 | jstor = 1576375 | publisher = The MIT Press | s2cid = 139028601 }}</ref> 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.

===Photo-etching===
{{Main|Photochemical machining}}
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.