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printech, January, 2001
RE: Solids Percentage in Inks


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From:Jeff Adrian (jeffadrian@johnroberts.com)
Date:19 Jan 01 08:39:39 -0600


Betty: Lithographic inks are comprised of ink oils, pigments and resins for the most part. The proportions do vary somewhat, especially so when comparing cold-set inks ( used on sheet-fed lithographic presses and web-fed business forms presses and newsprint presses) with heat-set web inks. It is the ink oil content of lithographic inks that is of environmental concern. These oils are the source of the VOCs, HAPs (a very small amount of HAPs), and particulates. Typically, cold-set inks have ink oil content between 15 and 24%. Heat-set inks have a higher ink oil content, typically 32 to as high as 40%. EPA accepts a substrate rention factor of 95% for cold-set printing and 20% for heat-set printing. The significant difference is due to how the inks dry respectively. Cold-set inks dry by chemical reaction (dryers formulated into the ink). Heat-set inks on the other hand dry by the application of hot air in dryers through which the paper web passes after competing its path through the printing units of the press. Because of the substrate retention factor, we must calculate this in to accurately determine the release of VOCs, HAPs and particulates to the atmosphere. Additionally, if there are air emissions controls on the heat-set printing presses (there often are), then this too must be factored in (the destruction efficiency of the controls) to determine net releases to the atmosphere. From the figures above, you can calculate the non-ink oil content of inks, and determine the percentage of combined resins and pigments for each type of ink. Again, these later components are not considered to be an issue from an environmental release standpoint. Hope this helps. Jeff Adrian



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