Web presses come in two major types: cold or “non-heat set” and heatset. Ink on pages printed by cold presses dries upon exposure to the air, while heatset presses include a special heater or drying lamp to cure the ink. Cold presses only work on uncoated paper with an absorbent surface, such as newsprint, while heatset presses can print uncoated and coated pages. This makes them a good choice for glossy magazine stock and inserts. Heatset presses often produce finer resolutions and crisper prints.
CMYK presses print using cyan, magenta, yellow and key black inks. They lay down dots of these primary colors to produce optical mixes that represent the rest of the spectrum. Cyan, magenta and yellow inks are all transparent and work only on white or very light papers. They work on coated and uncoated stocks, and can produce photographic results.
Spot colors are single color inks used to add a splash of color to an otherwise monochrome page. They are usually opaque and can print on white and colored substrates. Some printers use spot colors to match special colors, such as a company logo. In these cases, the web press may include CMYK and spot color printing in the same job. However, most presses require the operator to clean the press, change the inks and run the print job through a second time to accomplish this.
Web presses are fast and efficient for large jobs, such as daily newspaper editions, national magazines and book printing for large publishers. They're capable of producing up to 20,000 pages per hour, but they don't work well if you only need to produce a few prints. Offset web printing works best if you plan to run at least 5,000 impressions. For smaller jobs, sheet-fed offset presses are more efficient and cost-effective.