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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Etching | 4/5 | https://en.wikipedia.org/wiki/Etching | reference | science, encyclopedia | 2026-05-05T10:47:42.331695+00:00 | kb-cron |
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.
=== Photo-etching ===
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.
== Types of metal plates ==
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. Zinc is cheaper than copper, so preferable for beginners, but it does not bite as cleanly as copper does, and it alters some colors of ink. 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 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. With relatively soft copper, for example, the etching details will begin to wear very quickly, some copper plates show extreme wear after only ten prints. Steel, on the other hand, is incredibly durable. This wearing out of the image over time is one of the reasons etched prints created early in a numbered series tend to be valued more highly. An artist thus takes the total number of prints he or she wishes to produce into account whenever choosing the metal.
== Industrial uses ==
Etching is also used in the manufacturing of printed circuit boards and semiconductor devices, and in the preparation of metallic specimens for microscopic observation. Prior to 1100 AD, the New World Hohokam culture independently utilized the technique of acid etching in marine shell designs. The shells were daubed in pitch and then bathed in acid probably made from fermented cactus juice.
=== Metallographic etching === Metallographic etching is a method of preparing samples of metal for analysis. It can be applied after polishing to further reveal microstructural features (such as grain size, distribution of phases, and inclusions), along with other aspects such as prior mechanical deformation or thermal treatments. Metal can be etched using chemicals, electrolysis, or heat (thermal etching).
== Controlling the acid's effects ==
There are many ways for the printmaker to control the acid's effects.
=== Hard grounds === Most typically, the surface of the plate is covered in a hard, waxy 'ground' that resists acid. The printmaker then scratches through the ground with a sharp point, exposing lines of metal which the mordant acid attacks.