GRA 324 Lecture Notes - Sulfate, Starch, Sulfite
5 May 2013
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Topic 2: printing processes ring of ink around letter forms smooth edges/separated by chem. properties serrated edges/liquid may have a screen pattern in image areas; thick ink film metal cylinder screen frame. Raised image carrier is inked, then applied w/ pressure to a substrate. Image carrier: wrong reading (mirror image) made of metal. First/major printing process in use til 1960s lost to offset lithography. Less than of printing is done by letterpress: platen flat image carrier which open/close like a clam shell raised image is metal (lead) or wood cuts press can be used for perforating, scoring, die cutting. Usually web (roll) fed except sheetfed corrugated substrates. Wide range of substrates (plastic, bags, labels, etc) Major process used in packaging industry: planographic printing. Ink: oil based, thick, paste ink/water-based fountain solution. Image areas: attract oil but repel water (hydrophobic / oleophillic) Non-image areas: attract water but repel oil (hydrophilic / oleophobic)
