Why We Re-calibrated Our Thinking

This post will be useful for those of you who might be frustrated at the lack of consistent color quality control from your printer. A lot has changed in the press manufacturing industry in the last five years, yet it often goes unnoticed because printing presses appear to look so similar. From the outside, a six-color press built fifteen years ago looks very similar to a press built today. Where you really see the difference is when the side panels are removed. The amount of circuitry and wiring in today’s devices makes the Space Shuttle look simple in comparison. This is a good thing because it’s those electronic components which, among other things, allow the press to be managed remotely--usually from a control panel located near the paper exit area on the press.

In old-style, non-electronic presses (and there are an amazing number of these still operating today in even the most technology-forward printing operations), color quality and consistency is largely measured and managed visually. The better the pressman, or the less hurried and tired the pressman, the better the final result. That is why the level of craftsmanship was so important ten or twenty years ago. A printing company relied on the lead press operators and their physical ability to determine color quality.

But today’s digitally-enabled presses have changed the industry considerably. Now, virtually all aspects of press control from ink density to water and air (all critical to the printing process), can be managed away from the press itself. Modern printing companies and press operators rely much more on the digital control systems to ensure the press is running properly and with the proper balance of inks, water and air.

Here is how it works; After the press has been loaded with paper and printing plates, the press is ready to begin applying ink. These first sheets out are called "make-ready" and are recycled and not part of your production run. As these first sheets come off the press, the pressman will set the sheets down on a special work table. The edge of the paper closest to the operator is aligned with a guide strip and a device called a "densitometer" which automatically travels down this edge and “reads” the color bars which were printed on the test sheet. These color bars vary by printing operation and are defined by the software required to keep the press “in-color." This is where things can be a little different depending on the press being used.

At CCS Printing we use the manroland press workflow system. When we print our color bars we produce not only the standard CMYK (cyan, magenta, yellow and black) but also several boxes of gray scale ranging from solid to light. These gray boxes on our press sheets are very important and set the manroland workflow apart from many others. They also allow us to hold color throughout the press run. This means the hundredth sheet off press will match the last sheet out, even on a run of one hundred thousand.

To achieve this the press must be managed to “understand” the proper CMYK boxes being printed. It is even more important that it is able to distinguish a neutral gray color box. Neutral gray is defined as having no visible color. If there is a slight tint of magenta, yellow, or blue, then it is not a neutral gray. It needs to be mechanically tested by the densitometer to be neutral.

If the press is held accountable to producing a perfect neutral gray then we can guarantee all other colors in the press range will be accurate. To achieve that we measure the neutral gray color box each time the press operator pulls a test sheet from the press run. That information is electronically read by the densitometer and the information is passed to a PC workstation. There we look (digitally) for any variance in the gray. An electronic signal is sent to the press, which adjusts itself to match either ink, water or air to bring the press back into proper gray balance. This rather complicated concept explains the "GRACoL 7" standard which was developed by the IDEAlliance GRACol Working Group to create a useful standard for press calibration systems. This has now become the new industry standard in press quality color control.