Printing offset lithographic

Fig. 29.1. Mechanisms of letterpress, offset lithographic/flexo-graphic, and gravure printing processes.12...

As detailed earlier, offset lithographic printing operates on the principle that oil and water do not mix. With paper-based materials, conventional inks usually dry by oxidation and absorption. Early screen inks were also based on oil, drying by oxidation. These were used to achieve a thick film of 20-30 Pm. Thinner inks were obtained by the use of non-nitrated cellulose derivatives, modified resins and white spirit. Ultra-thin film inks were subsequently introduced which gave films between 5 and 10 Pm, thereby enabling the use of half-tone images. 

Certain attributes of the offset lithographic press make it particularly appealing as a means of mass reproduction of printed matter and images. These include extremely high throughput clear, clean, and sharp impressions the much lower cost of metal plates relative to stone plates the ability to handle rough and hard papers low... 

Uses Provides better coating coverage, improved wetting and dilution stability in printing industry when used in heat-set, offset lithographic printing processes as a topcoat on printed paper provides antistatic props. eliminates excessive ink buildup Features Usually diluted 40 1 with water exc. dilution stability good freeze-thaw stability... 

Cordeiro N., Blayo A., Belgacem N.M., Gandini A., Neto C.R, LeNest J.F., Cork suberin as an additive in offset lithographic printing inks, Ind. Crops Prod., 11(1), 2000, 63-71. 

Offset lithography is the most common process used for printing on paper. It is used for folding carton stock and for can and bottle labels. Most lithographic presses are sheet fed, although there are some web-fed presses. A particular application of offset lithography is the printing of flat metal sheets that are then... 

---