Printing methods

There are five types of printing techniques: planographic, stencil, relief, intaglio and digital.

Planographic is printed from a flat plate or stone and relies on the fact that greasy ink will resist water. It can be referred to as Lithography or simply Litho, from the Greek meaning stone. A drawing in a greasy, oil based medium can be made on a stone or metal plate which is then wiped with water and inked up. The ink will only adhere to the drawn surface, the plate or stone can then be put through a press in contact with paper and the image is printed. Offset litho is used for long commercial runs, newspapers and magazines for instance. In this process the image is first photographically transferred on to a roller, which is then rotated in contact with the ink roller and another to transfer the image to the paper. Because the ink is not transferred directly to the paper, greater consistency and faster printing can be achieved.

Stencil is the oldest form of printmaking and dates from the eighth century in China. A design is cut out of a substrate, paper or something more durable and then the ink or paint is painted or sprayed or pushed through it in some way. The most sophisticated form of stencil printing is screenprinting where the stencil is held on a fine nylon mesh and so very fine designs can be printed by forcing the ink through the screen with a rubber blade, called a squeegee. The most common way to make a stencil is to create a “positive” on acetate by digital printing or drawing and then to expose a coated screen to ultraviolet light with the positive between the coated screen and the light source. The black areas on the positive will protect some areas of the screen from the light and the coating can be washed away, while the areas that have been exposed to the light will have hardened and therefore won’t wash away, leaving areas where ink won’t pass through.

Relief printing includes woodcuts, linocuts, wood engraving and letterpress where ink is transferred to the raised parts of a block which is then pressed onto paper. Wood cuts are made by cutting away the parts of the design not wanted to be printed from a plank of wood, wood engraving is exactly the same but using the end grain of the wood, therefore overcoming any problems the grain of the wood might present.

In the mid fifteenth century Gutenberg revolutionised the book printing process in the West by inventing a machine which used moveable type, which meant that each letter could be reused over and over again in different compositions. By the end of the nineteenth century the linotype machine had been invented which was used for printing newspapers and magazines up until the 1980’s. With this machine an operator typed the text and above him, (invariably it was a him) was a process which cast each letter in lead and created solid blocks of text, slugs, which were in turn placed in a frame and a mould made and then recast in a more durable metal than lead to be put into the press.

Intaglio, from the Italian to carve (the G is silent as it is followed by an L), involves printing from the grooves made into a plate. The copper plate can be cut into with very sharp tools - this would be an engraving and is a very difficult task - or the plate can be etched which is a much easier printing process and which attracted artists rather than professional printmakers. In etching the plate is first coated with a resist of some sort, originally wax, and this is drawn into with sharp tools. No real force is required as one is just exposing the metal under the resist. The plate is then submerged in acid to ‘etch’ into its surface. The plate can then be worked on more, and submerged again, this time the new lines will be etched and the original ones will be etched deeper. The resist is cleaned off and the plate is printed in the same way as an engraving. Ink is pushed into all the grooves on the plate and then wiped off the surface. The paper is then dampened and put through a press with the plate. The press is usually a roller and a great deal of pressure is applied to force the paper into the grooves on the plate. If you examine an etching or engraving closely you can see the inked lines are actually slightly raised from the surface of the paper.

Digital printing is very clever and involves computers. Seriously though… giclée refers to an inkjet printer which essentially uses the same technology as your desktop office printer. Giclée means to squirt in French and refers to the spray of ink from the nozzles in the print head. One of the advantages of digital printing over other methods is that it can print a continuous tone without breaking it down into a ‘halftone’ of dots or some other shape. The difference between giclée and ordinary digital printing is that giclee uses many more colours than just cyan, magenta, yellow and black. The latest machines use eleven colours, and they use pigment based inks rather than dye which makes them much more resistant to fading in daylight. Also acid free paper should be used. Light jet (sometimes called C type) is a combination of conventional photographic printing and digital printing. A print head passes over the paper in the same way as a digital printer but it emits RGB light onto photographic paper which is then processed in chemicals.