Offset

Whether in terms of quality, speed, number of machines in operation, or printed tonnage, offset technology unquestionably remains the dominant technology in the printing industry.

From a technical point of view, offset is a printing process based on the repulsion of water and oil-based ink.

Conventional offset printing is based on water-oil repulsion which creates an oil-based ink/dampening solution emulsion. This is based on the antagonism between water and oil which do not mix. The engraved aluminium printing plate (image carrier) transfers the image to a blanket which in turn transfers ink onto paper.

Waterless offset printing uses plates where, roughly speaking, a silicone layer is substituted for the dampening (fountain) solution to repulse ink which is only deposited on exposed areas where the image should appear.

Rotary offset presses are fed with a roll of paper, and feature printing speeds of more than 45,000 copies of 96 pages per hour. Rotary presses are usually fitted with in-line finishing devices.

Sheet-fed offset presses print flat sheets with a size not exceeding 120x180 cm.

Press speed regularly increases and can reach 18,000 sheets per hour in large format. In parallel, make-ready times have been reduced tenfold in the last twenty years to reach record speeds thanks to automated systems and workflow management. 

In an increasingly competitive offset printing market, where decline in number of printed copies combines with buyers' continuous pressure on prices, constant progress is being made in automated systems and for the reduction of make-ready and lead times.

With the possibility of using direct tones in addition to the traditional CMYK inks, varnishes of all sorts, and very high resolutions, while maintaining relatively simple processes, offset printing allows to obtain the quintessence of printing quality nowadays.

From an economic point of view, advancements have restored offset printing competitiveness even for short runs, provided however they do not include any variable data. With its attractive cost per page due to very cheap consumables, inks and paper, offset technology has a long future.

By Patrick CAHUET, market expert and GRAPHITEC consultant