Relief Printing

About Flexography and Letterpress Printing Methods

Letterpress printing example; photo by borisforconi, CC by 2.0 license via Flickr.com
Letterpress (a type of relief printing) wedding announcement and printing plate. Image by borisforconi via Flickr.com; CC By 2.0 | Printing Terms | Alpha Index to Full Dictionary:. # | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | XYZ

The two types of commercial printing that are classified as relief printing are letterpress and flexography. In both cases, the image to be transferred to paper or other substrate is raised above the surface of the printing plate. Ink is applied to the raised surface, and then the plate is rolled or stamped onto the substrate. The relief printing process is similar to using an ink pad and rubber stamp.

Before the inventions of desktop computers and offset printing, most printing was some form of relief printing.

Although the image to be printed is raised on the printing plate, relief printing does not create raised lettering such as is found in embossing and thermography.

Flexography

Flexography printing is typically used for paper and plastic packaging including bags, milk cartons, labels and food wrappers, but it can be used on just about any substrate including corrugated cardboard, fabric and metallic film. Flexography is a modern version of letterpress. It uses quick-drying inks and is commonly used for long press runs. 

The flexible photopolymer printing plates used in flexography printing have a slightly raised image that receives the ink. They are wrapped around the cylinders of a web press. Flexography is well-suited to print continuous patterns, such as for wallpaper and gift wrap.

Flexography is a high-speed printing method. Although it takes more time to set up a flexographic printing press than an offset printing press, once the press is running, it requires little intervention from the press operators and is capable of running almost continuously for long periods of time. 

Letterpress Printing

Letterpress is the oldest form of printing. When offset printing was invented, it replaced letterpress as the preferred printing method for newspapers, books and many other printed products. Letterpress printing is now viewed as a craft, and it is still used and valued for limited edition art prints, limited edition books, high-end greeting cards, some business cards, letterhead and wedding invitations.

The hands-on process that once required assembling movable pieces of type in a frame now operates by making polymer plates using a photographic process. A digital design is imaged to film and then exposed on the plate. The unexposed areas of the plate are washed away, leaving only the raised areas that will receive the ink. The raised areas are inked and then pressed against the paper on a letterpress press, which transfers the image.

Most letterpress printing uses only one or two spot colors of ink. The presses run slowly compared to high-speed flexographic presses.