Artist’s Proofs are often marked ‘A.P’ or the French version ‘E.A’ (or E. d’A meaning ‘épreuve d'artiste’). Approximately ten percent of a print run are assigned as Artist Proofs. These prints are usually kept by the artist as a record of the print’s progression, but can also be released to market.
 
While there is no clear correlation between a print’s value and its status as an AP, some collectors relish APs because they are tied to an artist’s personal collection.

If a print is signed Hors d’Commerce or HC, it means this print was destined for promotional use. That is, it was intended as a sample for galleries or dealers. Again, there’s no explicit advantage to seeking out a HC proof, except if you are interested in the object’s ‘journey’.

This edition is usually held by the printer and can be signed by the artist. It operates as both a gesture of appreciation from the artist and a record for the printer.
 
Sometimes a printer will sell their gifted P/P because it constitutes a part of their payment and that’s how they end up in the marketplace.

The Trial Proof is created so that an artist can examine and perfect a work’s intricacies before commencing the grand print run. These trial impressions may not exactly mirror the final edition and some collectors may appreciate their unique nuances.

Aquatint is a process that was developed in the 17th century as a result of the desire to find a more delicate tonal range than etching offered. Hence, aquatints celebrate tone rather than line. Aquatints have an effect similar to watercolor. In this technique the plate is covered with a ground of resin, which is granular rather than solid, as in an etching. The surface is drawn upon with a stylus. The plate is then bathed in acid. The design, conceived wholly in tonal areas not line, is produced by protecting certain areas of the plate from the acid with an impervious varnish. Multiple bitings of the acid, as well as the use of several different resins with different grains, produce different degrees of darkness and tonal texture.

Cliché-Verre, or glass print, is different from every other print technique in that the image on the paper is not produced with ink, but with light sensitive chemicals. To begin the cliché-verre process, collodion or printer’s ink is used to coat a clear glass plate. A stylus is then used to draw the image on the coated plate. A sheet of photo sensitized paper is placed under the plate. The assemblage is then exposed to light (usually natural.) The image is transferred on to the photo paper in the same way that a photographic print is made from a negative. It is then chemically fixed to the paper. A more sophisticated version of this technique involves painting an image on the glass. The varying densities of the ink or paint appear of the final print as varying shades ranging from white to black. This technique was especially popular with the Barbizon artists including Corot and Daubigny.

Drypoint, which originated in the 1500s, offers the artist the most sensitivity in creating a line, from the most delicate hairline to the heaviest gash. Drypoint prints are created by carving a drawing into a metal plate with a needle or other sharp tool. As the plate is furrowed, metal shavings on each side of the incision build up—this is called the burr. In drypoint, the burr is not scraped away before printing. Rather, it remains on the surface of the plate and produces a velvety cloud of ink until it is worn away by repeated printings. Drypoint plates (particularly the burr on them) wear more quickly than etched or engraved plates; therefore drypoint allows for fewer satisfactory impressions and show far greater differences from first the impression to last.

Engraving is a process in which a drawing is done by incising a copper plate with a tool called a burin. The lines carved into the plates become furrows. As artists move the burin across the plate, copper shavings, i.e. the burr, are forced to either side of the lines being created. The burr is usually cleaned from the plate before inking. An engraved line may be deep or fine, and has a sharp, clean appearance that tapers to an end. Because this process is primarily based on line, shading is done by cross-hatching.

This process began in the early 1500's. Etchings generally celebrate line, rather than tone. An image is drawn by using a stylus, which scratches away an acid-resistant wax coating, i.e. the ground, on a copper plate. The plate is then covered in an acid solution. The scratched/exposed metal areas are chemically dissolved by the acid, creating grooves to hold the ink. Lines get deeper and darker depending on the amount of time the plate stays in the acid bath. Once the lines are carved, the ground is removed, ink is introduced into the grooves and a dampened sheet of paper is placed onto the plate and goes through a press. The press forces the paper into the grooves, yielding an elevated character to the lines, which is a signature trait of an etching. The stylistic quality of an etching varies depending on the tools and the type of wax used to coat the plate. This method is also relatively forgiving because it allows for corrections to be made while drawing in the wax on the plate.

Intaglio, which comes from the Italian word intagliare, meaning to incise, is the general term for printmaking techniques that rely upon the creation of an image through the carving of a metal plate, i.e. the matrix. Once incised, ink is then pushed into the grooves created in the plate. The rest of the plate is then wiped clean. The plate is put on a press bed with dampened paper on top of it. The plate is then run through the press under pressure and the ink in the grooves is drawn on to the paper creating the print. The paper used to go through the press is often slightly larger than the plate so the edges of the plate will be embossed onto the paper. The principle intaglio techniques are engraving, etching, soft ground etching, drypoint, aquatint, spitbite aquatint and mezzotint.

Liftground etching or sugarlift aquatint preserves the artist’s brushwork and allows broad areas of color to be reproduced as opposed to the relatively strict linearity of etching. In this method, the artist begins by painting an image on the plate with a solution of sugar and black ink. The entire plate is then coated with an acid-resistant varnish. When the plate is immersed in warm water, the sugar melts, and lifts away part of the varnish. The plate is then grained for texture, as in aquatint, and dipped in acid. Where the varnish has been lifted, the acid bites into the plate. In printing, ink gather in this etched area and creates a rich black tone on the paper.

Linocuts are made by cutting away areas out of a linoleum block, which is usually backed with wood for reinforcement. The linoleum is cut in the same manner as a woodblock; however, since linoleum is a relatively homogeneous surface and does not have grain, like wood, the print from a linocut will have less texture than a woodcut.

Lithography yields images that tend to be more painterly than those from intaglio techniques. Lithographs also share some qualities of colored pencil drawings, crayon or even pastel drawings. The process is based on the mutual antipathy of oil and water. To make a lithograph, the artist uses an oil-based medium, such as a crayon or tusche (an oily liquid wash), to draw a composition on a flat, ground stone. The surface of the stone is then flooded with water. The oily areas repel the water. Printer's ink, which is oil-based, is applied to the stone with a roller and, in turn, it adheres only to the sections which were marked by the artists with the oil-based medium. The water repels the printers ink elsewhere on the stone. The stone is then covered with a sheet of paper and run through a press to create the print. Though lithography literally means "stone drawing," in modern times the expensive and unwieldy limestone block has often been replaced by a grained metal plate, in which case the print is sometimes called a zincograph. The stone or plate, it should be noted, is not etched or engraved in any way but simply acts as a solid surface for the antipathetic actions of oil and water to occur. There are several specific types of lithographs. A transfer lithograph, or an autographie, as it is known in France, is one in which the original composition was drawn on paper made especially for the process and then mechanically (not photographically) transferred to the stone or plate. Color lithographs are made through the use of several stones or plates to separate the colors. The printing, however, is done on the same sheet of paper by using each stone or plate in turn. A lithotint is a lithograph in which the image is created on the stone with a brush and oil-based ink in the manner of a wash drawing. It is otherwise handled and printed exactly like a lithograph in which the artist uses an oil-based crayon. James McNeill Whistler worked extensively with lithotints.

Mezzotint is another technique that focuses on tone rather than line. It is a process that uses a negative process in which the artist essentially begins with a black background and by scraping or burnishing areas of the plate so that they will hold less or no ink, lighter tones are created. Because of its capabilities for producing almost infinite gradations of tone and tonal areas, mezzotint has been the most successful technique for the black-and-white adaptation of oil-painted images to the print medium.

Though often used interchangeably, a monotype and a monoprint have the following technical difference: in a monoprint there is a fixed matrix such as an already etched plate or stone that the artist manipulates or adds to in some way. This produces multiple unique impressions that are different in appearance from one another because it is virtually impossible to manipulate the ink the same way twice. Degas worked extensively with monotypes. Monotypes are usually unique, though sometimes a second, fainter impression may be taken from the matrix—this is called a ghost. They are made by taking an already etched and inked plate and manipulating additional ink on the surface of the plate. This produces an impression that is different in appearance from a conventionally printed impression from the same plate. Since it is virtually impossible to manipulate the additional ink the same way twice, every monoprint impression is unique. A monotype is made by drawing a design in printer’s ink on a smooth surface (often glass), the covering the surface with a sheet of paper, and passing it through a press. The resulting image will be the mirror image of the original drawing.

Photogravure combines the detail and intensity of photography with the painterly quality of lithography. While the photogravure print and the photograph share certain qualities, the photogravure print is fundamentally different because it is a vector-based image, i.e. it is comprised of thousands of tiny lines, rather than pixel- or dot-based, like a photograph. The photogravure technique begins with an original photograph. A transparency is made on glass from the negative of the original photograph. Through chemical processes, the transparency is transferred to and eventually etched into a copper engraving plate. Thus the original photographic image is etched into the plate. Finally, as in the other intaglio processes, the plate is inked, paper is laid on top and then pressed.

Planographic printing refers to those printing methods in which the ink of the final print lies flat on the paper, not raised or impressed. The principle planographic printing techniques are lithography, screen printing, digital printing, cliché verre, monotypes/prints and pochoir.

Pochoir is a direct method of hand-coloring through a stencil. Multi-colored pochoirs are produced with multiple stencils. The technique has often been used to add colors to black and white lithographs.

A group of photographs published together, usually with a unifying concept, such as artist, subject matter, theme, or composition. 

Relief printing requires the artist to use a negative technique to generate an image. Instead of simply drawing what he or she wants to be inked or appear as dark, the artist cuts out what he does not want to be inked, i.e. what he or she wants to appear as simply the paper or negative space. Because of this, relief prints tend to yield works of sharp tonal contrast—utter distinction between light and dark. A block is carved and then ink is applied to the block, which is then pressed on to paper. The portions of the block that are carved out and recessed do not receive any ink; hence the only remaining raised portions of the block show up as dark on the paper. The principle relief printing techniques are woodcut, linocut and wood engraving.

Andy Warhol was the first artist to extensively use the technique of screenprinting, particularily silk screenprinting. Previously, screenprinting had been used primarily for commercial advertising purposes. To make a screenprint, an image that has been cut out of paper or fabric is attached to a piece of tautly stretched mesh. Paint is then forced through the mesh (or screen) onto a sheet of paper beneath by means of a squeegee. The uncovered areas of the screen allow the paint to pass through onto the paper, while the areas covered by the compositional shapes will not. For works with more than one color, a separate screen is required for each color, or the same screen must be washed and remade each time. This technique is also referred to as Serigraphy.

Soft ground etching became popular in the 18th Century and the early 19th Century. It was used to emulate crayon drawings. The grounded plate used in this form of etching is made softer in consistency by adding some form of grease, like tallow. This is done so that instead of the artist having to use a hard needle-point, he/she may use a pencil to make the drawing in the ground. In this method, a sheet of thin paper is laid over the ground. The artist draws on the paper. Each stroke causes a line of the ground to attach itself to the paper. When the drawing is complete and the paper lifted, the portion of the ground that attached itself is pealed away and the copper plate is exposed correspondingly. However, it is uncovered in soft-edged, fluent lines for the acid to bite.

Spitbite Aquatint involves painting strong acid directly onto the prepared ground of an aquatint plate. The longer the acid is left on the plate, the darker the tone achieved. To control the acid application, saliva, ethylene glycol or Kodak Photoflo solution can be used. Traditionally, a clean brush was coated with saliva, dipped into nitric acid and brushed onto the ground, hence the term spitbite.

Wood Engravings are made from the end-grain surface of a very hard wood, usually boxwood, as opposed to woodcuts, which are made from the much softer side-grain planks of wood. The hardness of the boxwood, combined with the fine engraving tools used, allow for extreme precision and detail. As in woodcuts, it is the resultant uncut surface that takes the ink and prints. Thus, the inked areas which print on the paper define the lines which initially were engraved in the wood. Essentially these lines show up in the negative as the color of the paper.

Woodcut was developed in the 9th century in China and is the earliest form of all print techniques. Western artists began using the technique in the 14th century. Woodcut also played a central role in the development of the printing press. With the invention of movable type, a woodblock matrix could be set in the same press with the text, yielding books with printed text coupled with images. Woodcuts achieved a high level of artistic beauty in the 17th and 18th centuries in Japan, which is known as the ukiyo-e period. Woodcuts are made by cutting away areas in side-grain planks of wood with a knife. The areas that remain will be inked and the carved-out portions will appear as just the paper in the final product, a demonstration of the negative space