How Engraving Works
Engraving is a form of intaglio printing. An intaglio (in-tal’-yo) is a design carved into the surface of hard metal. Engravers create designs by cutting or “etching” fine lines into metal plates called “dies.” Historically these lines were hand cut, causing engraving to be labor intensive and costly. Since the late 1970′s engravers use photo-etching and other high speed techniques that enable the process to be timely, very competitive and affordable. These lines are filled with ink, and the image is transferred to a printing surface, such as paper, under high pressure.
THE EVOLUTION OF ENGRAVING TECHNIQUES
Engraving techniques appeared simultaneously in Germany and Italy around 1450, coinciding with Gutenberg’s introduction of the printing press. Maso Finiguerra of Florence and the early German masters, Schongauer, Graff and Albrecht Durer, were acknowledged early masters. Etching plates with acid was introduced at the beginning of the 16th century. Through a process called “stopping out,” some areas of plates are exposed to acid longer than others, allowing the artist to obtain rich gradations and delicate atmospheric effects. Rembrandt is considered the greatest etcher of this period.
Mezzotint engraving was invented in Germany in 1642. In a mezzotint, the engraver burnishes areas of a plate or die to produce an unlimited gradation of tone. Because this captures the effects of light and shadow so well, early mezzotint engraving was often used to reproduce famous paintings, broadening their audience and appeal.
Aquatint engraving, invented by Jean Baptiste Leprince in France, combines etched lines with clearly differentiated tonal areas. The result resembles the flat tints of an ink or wash drawing. Spanish artist Francisco Goya was the acknowledged master of the aquatint technique.
Contemporary Design Tips
Engraving is a skill-intensive discipline, but modern technological advances have made engraving economical, especially for large runs. In place of hand engraving, several mechanical and photomechanical plate-making options now exist.
Utilizes a template and mechanical tracing device called a router, which cuts directly into the metal. The depth of the cut can be adjusted and controlled, making it possible to create “raised” or “sculptured” surfaces.
There is no difference between preparing artwork for engraving versus offset printing. The process requires clear, shar reproduction art: either a crisp actual-size, camera-ready mechanical or black and white line art on disk. Pre-separate complex images on individual transparencies or files, as each color of ink requires a separate pass through the press.
For most automatic presses, the maximum plate size is 5″ by 9″, while the actual image area on the plate is about 4″ by 8″.
Specifying Inks For Engraving:
Water-based inks are the standard inks of today and create a matte opaque surface impression (with the exception of water-based metallics) and are generally quick drying and laser compatible.
Metallic Specialty Colors:
Metallic inks are available in three reflective colors: gold, silver or bronze plus a new array of pastel colors.
Caution should be exercised when specifying metallic inks for small, finite type, as the metallic particles used in these inks are not as finely ground as color pigments.
A rich surface gloss can be achieved by a second pass through the press to “burnish” the surface of the ink. Burnishing forces the metallic particles to flatten and reflect more light. It can also reveal extremely subtle details within the engraved image.
Specifying Papers for Engraving:
Engraved images may be reproduced on virtually any paper, provided the paper is strong enough to accept the pressure of the press. The high-tensile strength of cotton-fiber papers is ideal for engraving.
Compatibility With Other Processes:
If more than one printing process is specified, the engraving should be run last. This prevents subsequent processes from flattening previously raised engraved areas. Engraved printing is ideal for use in both laserjet and inkjet printers.
Since envelopes are not perfectly square and if precise registration is required, consideration should be given to engraving the envelopes on flat-sheet paper and then converting them to envelopes to preserve registration.
Consideration should be given to where the reversed image will appear on the back of the envelope in relation to the flap edges.
If no image is to appear on the back of the envelope, the flap should be lifted before stamping to avoid debossing on the flap.
Prior to engraving the plate, proofs should always be examined to verify that all of the image in the correct color is present. Press proofs are also available, typically for an additional cost.