Letterpress Printing - What is letterpress printing?
Definition of LETTERPRESS PRINTING:
A method of printing; this process creates an image through relief printing, using raised metal type or plates to compose the required image, before the image carrier is inked and the substrate pressed against the image carrier in order to transfer the image onto the substrate. The image carrier is made up of individual raised metal type (each of which carries an individual character), or a metal plate (carrying a line of text, a full page of text, or an engraved image), which can either lay flat or be wrapped around a cylinder (depending on the type of press used). While letterpress printing is commonly defined by its use of a metal image carrier, the process may use other materials such as wood and photopolymer plates.
The four stages of letterpress printing are composition, imposition, lock in, and printing. Composition involves selecting and arranging metal type to create a negative of the image being printed, before sections of a page or multiple pages are brought together (imposition), and then locked together to form one solid image that is then attached to the press. To print an image, the image carrier is coated with ink and pressure is used to transfer the ink from the image carrier to the substrate.
There are four types of letterpress presses; on a platen press the image carrier lies flat and a platen carrying the substrate lowers and applies pressure to transfer the image; on a flatbed press the substrate is carried on a rotating cylinder and the flat plate either sits beneath the cylinder or stands vertically; on a rotary press the plate is curved around a cylinder and the substrate is passed between the plate cylinder and an impression cylinder; and on a belt press there are two sets of plates, each carried on a separate belt, and the substrate is fed through the press twice to be printed on one side by one set of plates and then again to be printed on the other side by the second set of plates (this press is used predominantly to print books). This method of printing uses paste inks, which are transferred from an ink fountain by a fountain roller to a set of ink rollers (usually four), which then transfer the ink to a set of form rollers (usually three) that spread the ink onto the raised type on the image carrier. The ink is worked by the different sets of rollers to achieve the viscosity required to coat the relief areas (image) while leaving the recess areas (non-image) clear.
Letterpress printing is most commonly used to print monochromatic (usually black) text, but can also be used for colour printing; this process requires spot colours to be used and is best when printing only a few colours, each of which requires its own ink fountain and plate.
Letterpress printing is capable of printing sharp text up to a point; the process may struggle with very fine detail and usually requires text or an image to be of a minimum size or thickness. The use of metal plates can also create issues when transferring ink as it isn’t always possible to control the pressure that is applied in different areas, which can result in an uneven transfer of ink (a problem solved in modern letterpress printing by using flexible photopolymer plates).
Letterpress printing is one of the earliest methods of printing and remained popular from its invention in the 15th century, through to the 19th and 20th centuries, when it was overtaken by more modern forms of printing. In particular, flexographic printing often took over the role of letterpress printing due to its use of flexible rubber plates (rather than metal plates), which produced higher quality print at a lower cost. The process is experiencing a bit of a revival with a number of printers, hobby shops, and colleges and universities setting up their own letterpress presses. This method of printing was (and is becoming again) a popular way to print books and newspapers, invitations and stationery, and labels, and is capable of both web or sheet fed printing. It is capable of producing small and large volumes, and of achieving high printing speeds. UV inks can be used during high volume and high speed printing, to speed up the drying process and prevent smudging from occuring.Go Back to Glossary