Printing Resources
Learn about printing, proofing, and finishing operations, the ins-and-outs of paper, and find conversion charts useful to the graphic arts and printing industries.
Printing 101
Printing Overview
Printing methods and technologies have constantly evolved since Gutenberg printed his bible. The evolution continues today, as offset printing (the most widely used) is joined by digital printing throughout the industry. A number of other printing methods are also in use today because of the unique results they achieve.
Offset Printing
This most common commercial printing method relies on the principle that oil and water don’t mix. Once photographically applied to thin metal plates, image areas are chemically treated to make them ink-receptive and water-repellent. The non-image areas react oppositely.
During the printing process, ink and water find their respective places on the plate, and the inked image is transferred (or offset) onto a blanket (the rubber-covering on an intermediate cylinder) and then is offset again from the blanket to the paper, which is pressed between the blanket cylinder and a smooth impression cylinder.
Offset printing is generally used for large-quantity high-quality projects or those that must print with exact PANTONE® color matches. Lower-quantity projects are printed on sheets (sheet-fed) while rolls (web) can be used for higher quantities.
Digital Printing
A computer-to-print process, digital printing uses no plates or blankets, but rather employs an electrostatic charge along with heat to apply toner to the page. Digital printing allows for variable data printing, i.e., text and graphics can vary from one piece to the next without stopping the process.
Shorter set-up times, smaller page size and variable data capabilities make digital printing ideal for shorter runs, personalized direct mailings, and on-demand printing.
Letterpress
In one of the oldest forms of printing, lead or wooden letters are inked, and then pressed into the paper, leaving both the ink and an indentation. Today it is mainly used to add an antique or aged look to printed pieces.
Gravure
This is a very expensive process that skips the intermediate blanket used in offset printing. Provides amazing image reproduction, but is highly specialized and only practical in very large print runs. Paper money is printed using this process.
Thermography
Special powder is added to wet ink that has been printed using the offset process, and then dried under heat, which causes the image to swell, providing a faux-engraved look. Often used on business cards and stationery. It cannot be used for halftones or large solid areas.
Foil Stamping
A heated die presses a thin foil containing pigment (color, metallic, etc.) against the paper. The foil, in the shape of the die, remains on the paper. Opaque foil is often used to print a light image on dark paper. “Foil embossing” combines this process with embossing. Also see Embossing.
Silk Screen
Used for materials that can’t be put through a normal printing press (T-shirts, signs, etc.) A stencil with the image is applied to a screen made of silk, which is then pressed against the material to be printed. Ink is squeegeed across the screen, forcing the ink onto the material. This can be done by hand or machine.