One Type of Printing
One of the widely used printing methods these days is web offset printing. It is a printing method that makes use of a continuous roll of paper fed into the printing press. The sheets are only separated and trimmed according to desired size once printing has been finished. This method is intended for high volume printing such as newspaper publishing. It is a relatively modern development in the history of print.
Web Offset Printing – Overview
There are many variations of offset printing and web fed offset is just one of these. This printing method is called as such since the term “web” is used to describe rolls of paper that are fed to the printing press in order to produce continuous prints. The usual examples of materials printed through web offset presses are the following:
Generally, web offset printing is very useful when it comes to printing in long runs. Typically, it is the method of choice for press runs that are over 20,000 impressions. Speed is very important in choosing a printing method for press production. In such case, web offset printing is a good choice since some web presses can print about 3,000 feet a minute and even faster. Apart from the obvious benefits such as quick printing, some web offset presses also perform other tasks such as folding, cutting and perforating.
The ink that is used in web offset printing is the highly viscous type. Typically web offset inks have a viscosity of 40 to 100. Some of the typical examples are cold set, heat set, UV or ultraviolet and EC or energy curable inks. Heat set inks are the most common type and used for glossy and high contrast prints such as magazines. Cold set inks are generally applicable for books and newspapers and are an affordable option. EC and UV inks are among the highest quality inks that are set onto paper though the aid of light energy.
Two General Types
Web offset printing can be classified into two types which are the following:
Cold web offset printing is typically used for lower quality outputs. It is very common when it comes to production of newspapers. In this printing method, the ink dries into the printing sheet though absorption. The usual non heat set configuration comes with a series of peripherals and print units that are arranged in a vertical manner. However, newspaper markets are now seeking improved quality prints so some web offset presses today are now producing outputs with more contrast and gloss. Such web offset printing presses are adding heat set tower with dryers or UV based inks that cure on printing surfaces though polymerisation than absorption or evaporation.
The other type of web offset printing is heat set web offset which is a printing method that makes use of ink that dries through evaporation. This is possible with the aid of dryers that are placed right after each printing unit. This printing method is suitable for coated papers which produce a high and glossy contrast after printing since the ink remains on the surface.
The prints produced through heat set printing are typically hot for cutting and folding so chill rolls are positioned right after the dryers so that the ink set by configuring the paper temperature. The speed in which the ink dries up depends on the length of paper exposure to the temperature. This type of web offset printing is ideal for catalogues, magazines, inserts and medium to superb quality runs.