What is etching and how do you use a printing press?

Printmaking is the process of making artworks by printing, normally on paper. Printmaking normally covers only the process of creating prints that have an element of originality, rather than just being a photographic reproduction of a painting. 

Except in the case of monotyping, the process is capable of producing multiples of a same piece, which is called a print. Each print produced is not considered a "copy" but rather is considered an "original".

This is because typically each print varies to an extent due to variables intrinsic to the printmaking process, and also because the imagery of a print is typically not simply a reproduction of another work but rather is often a unique image designed from the start to be expressed in a particular printmaking technique. A print may be known as an impression. 

Printmaking (other than monotyping) is not chosen only for its ability to produce multiple impressions, but rather for the unique qualities that each of the printmaking processes lends itself to.

Prints are created by transferring ink from a matrix or through a prepared screen to a sheet of paper or other material. Common types of matrices include: metal plates, usually copper or zinc, or polymer plates forengraving or etching; stone, aluminum, or polymer for lithography; blocks of wood for woodcuts and wood engravings; and linoleum for linocuts. 

Screens made of silk or synthetic fabrics are used for the screen printing process. 

Multiple impressions printed from the same matrix form an edition. Since the late 19th century, artists have generally signed individual impressions from an edition and often number the impressions to form a limited edition; the matrix is then destroyed so that no more prints can be produced. 

Prints may also be printed in book form, such as illustrated books or artist's books.

Basic etching method

In pure etching, a metal (usually copper, zinc or steel) plate is covered with a waxy ground which is resistant to acid. The artist then scratches off the ground with a pointed etching needle where he or she wants 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. The plate is then dipped in a bath of acid, technically called the mordant (French for "biting") oretchant, or has acid washed over it. The acid "bites" into the metal (it dissolves part of the metal) where it is exposed, leaving behind lines sunk into the plate. 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.

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. 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.

Etching has often been combined with other intaglio techniques see Solarplate etching below

Solarplate Etching:

Printmaking with Solarplate is a simple approach and safer alternative to traditional etching and relief printing. Solarplate is a prepared, light-sensitive polymer surface on a steel backing for artists to produce fine prints. All one needs is inspiration, a graphic image created on a transparent film (acetate or glass), sun or UV light, and ordinary tap water, and the process is ready to begin. Both positives and negatives can be utilized; intaglio and relief printing techniques can be applied. 
The simple, spontaneous approach also makes it faster and more economical for use in professional printmaking workshops and collaborations with artists. Educators are replacing traditional acid techniques with Solarplate due to safety regulations. Being photographic in nature, Solarplate incorporates a broader range of techniques than any other printing medium.