Tuesday, July 3, 2012

Commercial Printing Processes

An understanding of printing processes is very important for any illustration commission, particularly for digital illustrations. With digital art, it is the illustrator or graphic artist who must create their illustration to be “print ready”. Even for non-digital illustrators, it is still important to know about printing processes. After all, the final outcome for an illustration or graphic design is the reproduced published image, not the original.

Letterpress Printing

Letterpress printing is perhaps the oldest form of commercial text printing in the western world, and although not nearly as popular today, it was the mainstay of producing publications for 900 years. It originated in China and it’s use dates back to the 11th century A.D. It migrated to Europe in the mid-15th century A.D.

Also called “relief printing”, type and images on a raised surface accept ink, which is then transferred directly to the printing paper. Because of the direct contact of the paper to the printing surface, the raised images appear in reverse, or “wrong reading”. Pressure is used to force ink to be transferred from the raised surface to the printed page. For this reason, letterpress prints presents a slight indentation when closely examined or touched.

Non-commercial application: Wood Block Printing and Linoleum Cut Printing.

Ink is transferred from a raised surface. © 2012 Don Arday

Offset Printing

Offset printing, also called planographic printing or lithographic printing, is now the most widely used method of printing. Lithographic printing was invented toward the end of the 18th century A.D. and gradually grew in popularity toward the last quarter of the 19th century A.D.

Lithography first employed the use of a thick flattened stone. The printmaker or artist would draw directly on the stone with a grease pencil or brush. Open areas could be kept clean with a solvent. The greasy areas would attract and hold the ink while water in the porous open areas of the stone repelled it.  In traditional lithography the printing paper contacted the stone directly, so as was the case in letterpress printing, images had to be drawn in reverse or “wrong reading”.

Commercial offset printing uses very thin zinc or aluminum plates that are coated with a light sensitized emulsion. Imagery can be photographically or digitally transferred on to the printing plate. Hardened areas of emulsion attracted ink while unexposed areas are washed away to repel ink. The printing paper does not come into contact with the printing plate. Instead the ink is “offset” onto a rubber blanket that then transfers the image to the printing paper. Hence the title offset printing.

Non-commercial application: Stone Lithography.

Ink is transferred form a resist surface. © 2012 Don Arday

Gravure Printing

Intaglio printing dates back to the 7th century A.D. in China and its forbearer, wood block printing, dates back to the 3rd century A.D. A more commercial form of gravure began to appear in the 17th century A.D. Gravure became even more widely used when it was combined with photographic processes in the 19th century A.D. The black elements on US paper currency including the finely webbed lines are an outstanding example of gravure printing.

Also called “intaglio printing”, or “engraved printing”, gravure involves having type and images cut or etched into a metal plate. The printing areas are the recessed parts of the image. Ink is then forced into the recessed areas and cleaned off of the raised surfaces. The printing paper is then pressed down onto the plate to draw the ink out of the recesses.

Non-commercial applications: Intaglio Printing, Engraved Printing, and Etched Printing.

Ink is transferred from a recessed surface. © 2012 Don Arday

Screen Printing

Some sources date “stencil printing” back as far as the 27th century B.C. However, the use of silk to form the stencil was developed in the 10th century A.D. in China. It was popularized and perfected in Japan in the 15th century A.D. And around that time it was adopted in Europe.

Silk fabric is stretched around a frame to become the substrate for the stencil. The applied stencil contains solid areas and open areas. Ink is then forced through the silk by a squeegee. The open areas of the stencil allow the ink to move through the silk to be transferred to a printing paper or fabric. The silk material comes available in a variety of densities. Very fine silks can be used to produce astonishingly fine detailed prints. Stencils can be photomechanical, digital, hand-cut, or even drawn or painted directly on the silk.

Non-commercial applications: Fine Art Screen Edition Printing and Mono-Print Screen Printing

Ink is transferred through an open surface. © 2012 Don Arday