Printing techniques: offset, digital printing and specialty printing

A media designer rarely delivers just 'a file' — the file must be produced on a specific print method and the method sets requirements for how the file is structured. At the same time the print method is a big part of the economy in a job: what's cheapest in 100 copies can be most expensive in 10000. That's why you need to know the main printing techniques well enough to advise customers and prepare correctly.

§Offset printing: the workhorse for large runs

Offset printing is an indirect printing method: printing ink is first transferred from a printing plate to a rubber blanket and then to the paper—hence the name 'offset'. Offset gives very high and uniform quality with precise color reproduction and is the standard for magazines, brochures, books, and other print in large runs.

The downside is the startup costs: printing plates must be made and the press must be set up before the first usable sheet comes out. This makes offset expensive for small runs—but because the actual printing is then fast and cheap per sheet the unit price drops significantly the more copies are printed.

§Digital printing: fast flexible and without plates

In digital printing, printing is done directly from digital data without printing plates or film. This removes the start-up costs, so small runs become cheap and quick to produce — often the same day. Digital printing also makes it possible to work with variable data: the content can change from print to print, so each copy can have its own name, its own address or its own QR code.

§Screen printing and flexographic printing: the specialists

Screen printing (screen print/silk print) pushes the ink through a fine-mesh fabric where a stencil blocks the areas that should not be printed. The method can apply thick opaque layers of colour to almost any material — textile glass metal plastic — and is used for t-shirts signs and special effects. Flexographic printing uses flexible printing plates and is widespread for packaging labels and corrugated cardboard where printing occurs on uneven or absorbent materials in long runs.

§Spot colours and special effects

Common four-color printing mixes all colors of CMYK. A spot color, on the other hand, is a pre-mixed printing ink – often defined in a color reference system like Pantone – that is printed in its own printing unit. Spot colors are used when a brand color must be hit exactly, or when colors are desired that CMYK cannot reach, such as clear neon colors or metallic. In addition, there are post-treatments such as partial varnish, foil printing, and embossing that give the print product tactile and visual effects.

§Paper and materials

The printing method is never chosen in isolation from the material. The paper's surface (coated or uncoated), its weight and colour affect how the ink sits and is perceived — the same design looks markedly different on glossy magazine paper and raw, uncoated paper. For large format such as banners, posters and signs, specialized printers are also used which have their own requirements for resolution and file setup. Discuss paper choice and material with the printer as part of the task, not as an afterthought.

§What does the method mean for your file?

• 01Clarify printing method and printer before preparing — requirements for profiles, drainage and colours vary.
• 02Use only spot colours if they are actually to be printed as spots — otherwise they will be converted to CMYK.
• 03For screen printing and foil/lacquer effects are typically supplied as separate, pure vector surfaces.
• 04With digital printing with variable data, the data source (e.g. name list) must be agreed and proofread.
• 05Ask about colour proofs on colour-critical or expensive productions before the whole print run is done.

“The best printing technique is not the finest — it is the one that fits the print run, material, deadline and budget.”

— Basic rule in production planning