Today, printmaking is a respected form of fine art. In the past it was a powerful way to communicate news, religious doctrine, and instruction to the public.  Printmaking became a more prominent art form as artists discovered its potential and as communication techniques evolved. Printmaking is a unique artistic form that creates artwork by printing (transferring ink from a matrix), commonly onto paper. The medium of matrices varies widely depending on the printmaking technique utilized, but can include wood blocks, linoleum, and assorted metals such as aluminum or copper, silk screens, etc. According to The Printmaking Bible, there are five main areas of printmaking: intaglio, relief, lithography, screen printing, and monotype. The International Exhibition of Northwest Printmakers included countless prints representing each style, as well as mixed media prints in the later exhibitions. Mixed media printmaking can be more experimental and can incorporate more than one traditional technique, as well as other forms of artistry.  Printmaking techniques can be very individual as artists will develop their techniques to meet their needs and expectations, however, the following broadly describes the five traditional printmaking processes. 
Intaglio is an Italian word meaning "to engrave" or "cut into." Printmaking utilizing intaglio techniques involves incising or gouging lines into the surface of a metal plate and filling the marks with ink in order to transfer the image to paper. Etching, engraving, and generally, collagraphy, are forms of intaglio. Etching involves the use of acid to incise the lines into the metal, while engraving generally uses a carving tool called a burin to engrave the image into the metal. The International Exhibition of Northwest Printmakers included numerous printmaking methods using the intaglio process including aquatint and softground (techniques used in intaglio etchings), drypoint and mezzotint (methods used in intaglio engravings).
Relief applies an opposite technique to intaglio because the image is engraved onto the medium, traditionally a block of wood or linoleum, and the areas that have been cut away will not print, as the ink will lay on the raised surface. Throughout the years, the exhibitions featured prints using the relief process including woodcuts, wood engravings, and linoleum cuts (commonly known as linocuts).
Lithography uses grease to draw an image directly onto a stone or metal plate where the print is then pulled from the stone due to the fact that the ink is attracted to the grease. Color lithography and lithograph-assemblage prints were among many of the prints shown at the International Exhibition of Northwest Printmakers.
Screen printing uses a fabric stencil technique, where the fabric is stretched across a frame and color is forced through the stencil against the surface of the paper. Silk screen prints, also known as serigraphs, were also featured at the exhibitions.
Monotype prints were less ubiquitous than intaglio, relief, and lithography prints, but were occasionally featured in the International Exhibition of Northwest Printmakers throughout the years. Monotype derives its name from the idea that the creation of the image both on the printing surface and the matrix cannot be replicated, and thus, the work is singular. The matrix can include materials such as glass, acetate, or the back of a metal plate. Marks onto the matrix are created using brushes, rags, hands, or other objects.
 Ann D'Arcy Hughes and Hebe Vernon-Morris, The Printmaking Bible (San Francisco: Chronicle Books LLC, 2008).
 Ibid. and "Printmaking," Wikipedia the Free Encyclopedia, https://en.wikipedia.org/wiki/Printmaking#Mixed-media_prints (accessed March 14, 2020).
 Definitions were derived from The Printmaking Bible and the Wikipedia "Printmaking" entry.