As the number of establishments using offset plates reduces, plate volumes remain stable or show slight increases due to the proliferation of multi-unit presses, shorter print runs performed more frequently and vast improvements in the time it takes to change-over plates, or make ready as it is known.
The SRA3 plate market is the one most affected by digital printing. Digital presses offering duplexed 2-up A4 printing on-demand without the use of offset plates, have almost replaced the old ‘small offset’ market. Most quick printing outlets today have waved goodbye to their AB Dicks, Iteks, TOKs and even GTOs in favour of digital cut sheet presses from manufacturers such as Fuji Xerox. Having said that, there is still a strong stalwart community of ‘52cm’ press users where the delights of digital are not needed. Heidelberg has even given its 52cm press range ‘Speedmaster’ functionality, plus anilox, and dropped GTO altogether.
The B2, or 4-up, sheet size market is different and only recently have we seen digital versions in this format. The B2 sheet is the most widely used in the offset printing industry and, therefore, plate sales are still robust. B1 (8-up) and larger presses are of course still the exclusive domain of offset, perhaps until Drupa 2016 when we may possibly see commercialization of Landa Nanographic machines.
So, the offset plate market has changed dramatically in the past 10 years. Like all sectors of the imaging industry, plates have had to keep up with technology demands. Computer to plate making, without the use of a film negative or positive, is one of the biggest change-agents. Environmental demands to reduce chemical and energy use is another. Platerooms, once an alchemist’s labyrinth of darkrooms, toxic fumes, chemicals, films and light sources are now so clean they can be in an office environment.
These advancements have changed offset plates from simple pieces of imaged metal—the ‘final interface’ between ink and paper—to part of a sophisticated system designed to take page data, usually PDF, transform it into printable signatures and finally output onto digitally imaged plates that can be either thermal (IR) or violet in sensitivity—both extremes of the visible spectrum.
The Plate System Explained
Printers today do not frequently chop-and-change between plate suppliers due to this holistic system approach. The ‘system’ should include:
A workflow that does justice to the final plate output and takes in functions such as trapping, imposition, dot gain, colour management, rendering, overprints, spot colours, coatings and the increasingly popular ‘ganged up’ printing where multiple jobs are printed on one sheet, minimizing paper waste.
The CTP machine and Rip. The CTP device will be imaging either thermally activated or light-activated silver halide plates. The laser or LEDs need to be adjusted to perfectly match the plates being imaged.
Proofing: whether hard copy proofs or measured on-screen ‘soft’ proofs are used, clients mostly want to approve the job before printing. Knowing plate characteristics will enable more accurate proofing.
The plate processor or ‘processless’ sub-system. Even plates that use no or low chemistry to develop and fix the image use water. Minimising water usage and, in a low-chemistry situation, replenishers, not only reduces environmental impacts but can save sizeable amounts of money. Processless plates that come out of the CTP and are mounted straight onto the press, bypassing the processing stage, are increasingly popular, but they still require washing-out of the non-image area, something that is accomplished with a balanced fount solution and a few initial sheets. Again, the system approach will ensure efficient washout and on-press performance.
All plates will of course work in various workflows, with different Rips and with different brands of compatible CTP. The difference with a ‘system’ approach is that there is always a support structure that takes responsibility for the whole process—to set plate production up correctly and to keep it at peak performance.
Plate trials are perhaps the best way to assess whether a new system will deliver the required benefits. Three Australian Printers—Worldwide Printing, Terry Howe Printing and Ink On Paper—discovered this when they were experiencing problems with their processless plates. Their stories can be seen here.
One comment from Terry Howe reads: “We changed over to Fujifilm Pro-T3 plates and have not looked back. Our production is back into full flight, and when we receive new consignments of plates, the batch-to-batch variance is minimal. Even the way the Pro-T3 plates are packaged is sturdier so they remain flat and easier to handle.”
There are many such stories where printers have successfully accessed the systemized, analytical approach to using offset plates instead of just purchasing boxes of sensitized grained aluminium sheets.
As with the human body and medicine, the ‘Holistic’ approach works best for plates, too.