Offset lithography rollers

Figure 10.2 Offset lithography rollers. (Drawing courtesy of Boris Listdat.)... 

Their main disadvantage is that the heat of vaporization of water is greater than that of the organic solvents usually used, e.g., 1043 BTU/ lb as compared with about 180 BTU/lb for toluene, methyl ethyl ketone, and ethyl acetate. Also, the utility of these inks is limited they cannot be used in letterpress printing because they dry too rapidly on open roller systems, and they cannot be used in web-offset lithography because they are miscible with the aqueous fountain solution. Moreover, the water may swell the paper substrate and give poor register, and paper printed with some water-based inks cannot be recycled in the presently-used processes. 

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