Nowadays, two different processes are used in web offset printing: heatset and coldset.
The coldset process is mostly used to print newspapers and paperbacks, with the printing ink drying purely by absorption.
In the heatset process, the paper is passed through a large dryer and a chill roll unit after the last printing unit. The length of the printing press is almost doubled by these two units. To ensure that the ink dries optimally, special heat-drying inks are used here.
Fogra is currently working with great commitment on modernising ISO 12647 and adapting it to current environmental conditions.
Important innovations of the reformed ISO 12647 will be:
- Innovations regarding paper types (PT)
- New tone value increases
- For proofing: New papers with optical brighteners
Why is ISO 12647 being revised? Environmental conditions have changed significantly at three central points since the last revision in 2004.
The previous paper types 3 and 5 with the paper whites defined in 2004 are hardly available on the market today. Even picture printing papers today show a much stronger blue colouration than just a few years ago. In addition, the revision of D50 in 2009 means that the lighting in the pressrooms now also contains considerably more UV than before 2009, which has caused problems in the matching of proofs without optical brighteners compared to papers with a high proportion of brighteners. Instead of the previous 5 paper types, there will probably now be 8 new paper types which also differentiate between glossy and matte picture printing paper:
- PT1: Coated picture printing paper (Premium coated)
- PT2: Brightened, coated picture printing paper (Improved coated)
- PT3: Glossy coated magazine paper (Standard coated glossy)
- PT4: Matte coated magazine paper (standard coated mat)
- PT5: Wood free uncoated
- PT6: Supercalendered, uncoated
- PT7: Improved uncoated paper
- PT8: Standard uncoated
Based on these eight types of paper, a total of 16 printing conditions are created by using frequency modulated non-periodic screening and conventional periodic screening.
The Moiré effect, or in other words a halftone screen overlay, is a common phenomenon when viewing prints. It occurs when two even patterns overlap unevenly.
When does Moiré appear?
Moire is always created when screens overlap. Typical examples:
- You have scanned in a newspaper ad and print it in another newspaper.
- You print the portrait of a managing director wearing a jacket with a fine houndstooth pattern, a checkered shirt and a finely patterned tie. Regardless of the printing process, complete moiré chaos is guaranteed to break out here.
- A brick building is reproduced in offset printing.
- The photograph of a ventilation grille is viewed on a monitor Continue reading