Print explained: offset litho vs. digital

By Lucy Batley

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Print explained: offset litho vs. digital

Before printing, monks would painstakingly handwrite copies of the bible and religious scriptures. Knowledge was confined to the very few who could read and write, therefore education was scarcely available.

The invention of printing is considered one of the most important advancements in human history as it gave knowledge freedom. For the first time, people were able to communicate and educate. The written word, now published on an industrial scale, became available to the masses. This encourages a culture of education, invention and innovation

Today, two main types of printing method exist; Litho and Digital.

This document will explain when each process should be used and why.

Offset Litho Printing

What is Offset Litho?

Offset Litho is a method of printing at an industrial scale in which inks are transferred onto aluminium plates to make an impression.

The process:

1) All printed colour images are made up of primary colours: CYAN (blue) MAGENTA (red) YELLOW and the Key colour Black (CMYK). The design (artwork) is set-up on a computer and all the colours on the artwork are separated into CMYK and sent to the plate making facility.

2) The artwork, now split into 4 individual colours, are exposed just like a photograph onto photosensitive aluminium sheets, known as ‘Plates’.

Each Colour = 1 Plate

3)  The Plates are collected by the printer and inserted into the press by clipping onto a roller.

Each plate is coated with its corresponding colour by a smaller ink roller. The coloured image is rolled or ‘offset’ onto a cylinder (blanket), which makes an impression on paper being fed through the press.

As the paper moves through each set of rollers, the colours mix to create a full-colour image on the page.

4) The pages are guillotined and collated. They are then taken to the finishing department for binding, punching, numbering etc.

When would Litho be used?

Because of the various processes involved, Offset Litho printing can become costly. This method of printing is best suited for larger quantities of printed pages, such as: books, magazines, newspapers etc.

An advantage of Offset litho is the ability to use spot (PANTONE) colours in the same way a process colour (CMYK) would be used. Spot colours are standardised, which ensures consistency. For example, a Red 032U printed in China will look identical to a Red 032U printed in England (providing they are printed on a similar paper).

Spot (PANTONE) colours are important for companies who want to ensure complete brand consistency on all their printed material, such as letterheads.

Spot can also achieve colours that CMYK can’t, such as bright orange, fluorescent pink, gold etc.

Digital printers are unable to print spot colours and so the hues and tones of the inks will differ from printer to printer.

Offset litho also offers a higher quality print and can print large areas of solid colour.

In summary:

  • Cost-effective at Large Quantities
  • Better Print Quality
  • Print on a large variety of stock
  • Print Spot (PANTONE) colours
  • Print large areas of solid colour

Digital Printing

What is Digital Printing?

Digital printing methods include inkjet or laser printers that deposit pigment or toner onto the paper.

The process

Unlike Offset Litho, the digital process does not require the use of plates and so it offers an earlier and faster method of printing. Although the cost per sheet is higher using digital, this price is offset by the cost saving of avoiding all the technical steps, time and personnel required to print Litho.

Digital Presses use CMYK process colours, unlike Litho, however, they are applied at the same time by the machine.

Quite often Digital presses have the ability to cut, collate, and bind too, saving huge amounts of time and effort.

In summary:

  • Cost-effective at Smaller Quantities
  • CMYK Process Colours
  • Reduced Quality
  • Limited choices of stock
  • Faster turnaround

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