- There is no need to adjust ink-and-water balance, allowing fast startups.
- Few process variables means minimal newsprint waste.
- It is forgiving of inaccurate press settings (wide press latitude).
- Letterpress produces ink mist.
- Ink laydown is not smooth, leading to blotches, streaks and spots in solid areas (mottle).
- Halftone images are coarse.
- Press configurations are limited, since there was less demand for color when most letterpress presses were installed.
- Ink sometimes bleeds through to the opposite side of a page (strikethrough).
- Letterpress requires high paper tension, which means that paper must be relatively strong (high basis weight).
- If set to standard densities, flexo ink does not rub off.
- Flexo produces bright colors.
- It also produces clean and high-contrast images (no toning).
- It generates less newsprint waste than offset lithography.
- It is less complex than offset.
- It is well suited to lightweight newsprint.
- Maintaining ink viscosity is critical, and flexo is relatively unforgiving of inaccurate press settings.
- Because of this, press operators must be highly skilled.
- The soft flexo plates wear quickly.
- Plates and other consumables are expensive.
- There are a limited number of plate and ink suppliers.
- Differences in blade and roller wear can change ink densities from page to page.
- Offset has by far the largest installed base at newspapers, making it the de-facto industry standard.
- Offset ink does not mist under normal operating conditions.
- Offset is capable of producing sharper (higher-resolution) images than flexo.
- It has the lowest plate cost of any of the three technologies.
- It produces smooth solids due to the offset action of the printing blanket.
- Platemaking is fast.
- There are many suppliers of hardware and consumables.
- Offset may leave ink set-off on adjacent pages, especially process-color pages.
- Like letterpress, offset falls prey to rub-off, though newer inks are reducing that problem.
- Offset generates relatively high startup waste.
- It is prone to print defects such as toning, tinting and scumming.
- Unlike flexo, it may be difficult to maintain balanced inking across a page with inking systems based on page packs and inking columns.
Process Pros and Cons
When shopping for a new press, it is important to understand the pros and cons of the three major newspaper-printing processes. Here's a quick-and-dirty checklist to get you started.
Letterpress
It's not likely you'll be buying a letterpress anytime soon, unless you purchase one from among the roughly 5 percent of North American newspapers still using them. Letterpresses use relief-type printing--a process that, like a hard rubber stamp, prints off raised characters using simple oil-based inks. They had their heyday between the late 1940s and the late 1960s.
Pros:
Cons:
Flexography
Like letterpress, flexo is based on a relief plate, although the plate is softer and uses a lower impression pressure. Unlike letterpress, flexo ink is water-based. Newspaper presses can be either full flexo or "sprinkled flexo"--part flexo, part letterpress.
Pros:
Cons:
Offset Lithography
The underlying principle of lithography is the old cliché, "Oil and water don't mix." While the image areas of the plate love the oil-based ink, the non-image areas are water-receptive and reject the ink. The image is transferred (offset) from the flat-surfaced, or planographic, plate to a rubberized blanket cylinder and then to the newspaper sheet.
Pros:
Cons: