Printing Methods used on Illustrated Advertising Covers
Presented by Michael Heller
Overview of Printing Methods
There are essentially only three different basic types of printing methods:
Relief printing – Ink is carried on raised parts of the printing surface.
Recess printing – Ink is picked up from grooves cut into the plate.
Planographic printing – Ink is picked up from the surface of the printing plate.
Relief printing – In this method, the design on the printing base consists of raised areas, to which ink is applied. The print is created when pressure is put on the back of the paper and ink is transferred to the paper from the raised areas of the printing base.
Two forms of relief printing used in the 19th century were woodcuts and wood engraving. The woodcut technique is one of the oldest forms of relief printing, dating back to the ninth century in China and the fourteenth century in Europe. A woodcut is made using the soft side-grain or plank side of a block of wood. The design is either drawn or painted directly on the wood block or pasted on it. The area all around the design is then cut away, with the raised ridges forming the black lines of the print. Given the soft nature of the wood surface, there is a tendency for the wood to crumble after repeated use and it can be difficult to achieve fine detail in the print.
Invented in the late eighteenth century, wood engraving is a variation of the woodcut. Here, the wood is cut cross-grained rather than plankwise, with the end-grain block used to produce more intricate work. Using a tool similar to an engraver’s burin, the wood-engraver incises lines into the hard wood, rather than cutting away wood to leave lines exposed. In contrast to the woodcut method, wood engraving can produce very detailed prints. Note that, in spite of the term “engraving”, the latter method is a relief printing process.
The majority of prints found in books and newspapers of the 1800’s were produced by wood engraving. Although many of the prints were drawn on the wood itself, by the 1860s, it became common to project a photograph of an image onto the wood block, with the surface sensitized in a manner similar to a sheet of photographic paper.
Typography (or letterpress) is a form of relief printing used to produce postage stamps. Ink is applied to the raised letters in the plate and pressure is used to transfer the design to the stamp paper. Examples of typography include certain Postmaster Provisionals; a few Confederate issues (#6, 7 and 14); and most overprints on stamps.
Intaglio printing – This labor-intensive and expensive process requires an engraver to cut a design into a stone or metal base (usually copper or steel) using an engraving tool known as a burin. The deeper the cut, the wider the print. By varying the depth and width of the engraved lines, the engraver can produce what appears to be a three-dimensional print, with tonal areas.
Ink is applied to the printing base, which is then wiped, leaving the surface (the non-printing areas) clean. Ink is effectively held in the recessed areas and transferred to the damp paper by applying pressure through the back of the paper. This results in a very detailed printed design, which appears slightly raised above the surface of the paper. As the damp paper is essentially pushed into the grooves of the plate, the back of the paper may appear somewhat embossed. This process was used to prepare most U.S. postage stamps during the first 120 years.
Most engraved prints include some degree of etching. Here, the top of the plate is coated in wax, while the back is painted with varnish. The design is drawn in the wax, cutting through to the surface of the plate. The plate is then immersed in a bath of acid, which eats away the exposed portion of the metal plate, resulting in etched lines.
Photogravure – The design to be printed is first photographed through an extremely fine screen. The screen breaks up the photo into tiny dots, which are then etched (with acid) into the plate. Like intaglio engraving, the ink is lifted out of the etched areas when the paper is pressed against the plate. Unlike intaglio engraving, the ink does not appear raised relative to the surface of the paper.
Lithography is the most common form of planographic printing. This printing method relies on the chemical fact that oil and water will not mix. It first involves the drawing of a design in greasy ink on a flat surface (generally a stone or metal plate). The surface is then wetted with acid or some other ink repellent fluid, which essentially confines the printing ink to the greasy lines of the design. The ink on the printing area is then transferred to the paper by pressure. Relative to intaglio engraving, the printed design appears dull or flat.
Offset Printing (offset lithography) – Greasy ink is applied to the dampened plate and an impression is made on a rubber blanket. Paper is then pressed on the blanket, which picks up the ink. The process and results are very similar to traditional lithography.
U.S. stamps produced by lithography include: Post Office seals; the first five Confederate States general issues; and postage stamps from 1918-1920.
Cameos: One of the most desirable types of illustrated covers is the cameo illustration. As opposed to a typical illustration that shows the detail with black lines against a white background, the cameo type of illustration is reversed – the positive image is white and the background is colored. Most cameos appear to be relief printed (i.e., wood engraving). This type of illustration was widely used in the 1850s and is considered one of the classical forms of illustrated advertising.
Embossing is the raising of parts of the surface of a piece of paper, through the use of a die stamp. In this process, a design is first cut or etched into a plate. Then a second plate is made with the same design in relief (i.e., with the design raised above the printing plate). The embossed design is produced when paper is placed between these two plates and they are put together under pressure, which forces the relief part of the second plate into the recessed portions of the first. Many cameos are also found with embossed lettering and/or illustrations.