Sunday 16 November 2008

offset lithography

The main print process i would use in my project is offset lithography. This is the most commonly used print process, where an inked image is transferred from a plate to a rubber blanket and then onto the printing blanket. The offset technique employs a flat image carrier on which the image to be printed obtains ink from ink rollers, while the non-printing area attracts a water-based film (called "fountain solution"), keeping the non-printing areas ink-free.

Offset printing advantages

Advantages of offset printing compared to other printing methods include:

  • Consistent high image quality. Offset printing produces sharp and clean images and type more easily than letterpress printing because the rubber blanket conforms to the texture of the printing surface.
  • Quick and easy production of printing plates.
  • Longer printing plate life than on direct litho presses because there is no direct contact between the plate and the printing surface. Properly developed plates running in conjunction with optimized inks and fountain solution may exceed run lengths of a million impressions.
  • The more you print, the less you pay per page, because most of the price goes into the preparation undergone before the first sheet of paper is printing and ready for distribution. Any additional paper print will only cost the client paper price (and ink), which is very minimal.

Offset printing disadvantages

Disadvantages of offset printing compared to other printing methods include:

  • Slightly inferior image quality compared to rotogravure or photogravure printing.
  • Propensity for anodized aluminum printing plates to become sensitive (due to chemical oxidation) and print in non-image/background areas when developed plates are not cared for properly.