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Fwd: Re: Metals in Printing Ink




X-Sender: wjw5@email.psu.edu
Date: Thu, 8 Aug 2002 10:47:08 -0400
To: Listman <listman@wmrc.uiuc.edu>
From: Warren Weaver <wjw5@psu.edu>
Subject: Re: Metals in Printing Ink

Rusty,

I used to work in the printing industry so I believe the following response to be an accurate one.

Lead chromate yellow was still the yellow pigment of choice in the early '70s. By about 1975 or 76, it was phased out in favor of diarylide yellow, an organic pigment with no metal components. That's what is used to print comics and all other newspaper inserts today. The blue pigment used to print comics and other lower cost, lower quality inserts is iron based (iron blue or ferric blue)-was then and still is. The red pigment is barium based-again no change. Its called barium lithol red. Black is, of course carbon black, totally organic.

Color inserts today are printed with one of three processes-offset lithography, flexography and rotogravure. Most-60+%-are printed offset. Fewer, but still a significant minority-perhaps 30% + or - are printed with gravure and a very small portion-perhaps 2 -3% being printed with flexography and virtually all of them being Sunday comics (about 30% of all comics are printed with flexography). The inserts printed with offset use oil based inks. Those printed flexographically use water based inks. Those printed with gravure use solvent based inks.

For products printed on the lower end of the quality spectrum, the same 4 pigments are used with all three printing processes (though the way the pigment is prepared for making the inks is different for each). With some of the higher end products (though not frequently used for newspaper inserts because of the added cost), the yellow, red and black pigments are the same, but the blue is different. Incidentally, newspapers use inks with the same pigments as comics.

Higher quality printing such as magazines and a small minority of newspaper inserts use the same red, black and yellow pigments, but a higher "cleaner" grade. The blue pigment, however is different...and significantly more expensive. It is copper based. Iron blue can't be cleaned up enough to obtain the quality of printing on coated paper that is desired for magazines. Instead, magazine inks are made with a copper-based pigment. These inks are known as "copper blue", "cyano blue" or just cyan.

All of these pigments are quite stable, though they break down when reacted with strong acids, as in the case of a TCLP test. This has not been an issue except for the cyan pigments since copper is released and detected in a TCLP test. Thus a waste stream containing cyan pigment might be considered hazardous if copper is present in significant quantity (rarely the case). Lead chromate yellow was, of course an EH&S issue in the '70s. The only one that's been an issue over the last 25 years is cyan, and even then it was not a major concern.

Hope this is helpful.

Warren


Forwarded on behalf of Rusty Harris-Bishop.  Please reply to p2tech@great-lakes.net.


I have a question regarding the color inserts in newspapers (I believe it's a flexographic process). Does anyone know if they still use metal inks in printing these? Does anyone know when they were phased out if they were? I have looked on the print-tech archives, and didnt' see it answered, and posted a question, but it didn't seem to get a response.

Anyone have any suggestions?

Thanks

Rusty Harris-Bishop

NC DPPEA

rusty.harris-bishop@ncmail.net

www.p2pays.org



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