Printech Archives, November 1997: Re: Heatset Web Offset Dryer Smoking

Re: Heatset Web Offset Dryer Smoking

Jeff Adrian (
17 Nov 97 08:22:18 -0600

Opacity issues are quite common to heatset web presses that do not have
emissions controls on their dryers. Opacity is usually greater right at
press startup. Depending upon ink loading, a combination of ink coverage and
press speed, opacity will continue to be an issue during the press run
itself. What you are observing as "smoke" are VOCs that are derived from the
ink oils in heatset inks. Most heatset inks contain approximately 32-40%
ink oil. Additionally, the EPA-acknowledged substrate (paper, usually)
retention factor is only 20%, meaning that 80% of those ink oils are assumed
to be released from the dryer to the atmosphere, unless controlled by
catalytic or thermal oxidizers of some type.

Depending upon environmental regulation in a given area, and its
enforcement, exceeding the legal opacity levels will likely result in enforcement
that can be costly in terms of fines. So even if a heatset press operation
at a facility is "grandfathered" in for open stack operation, not very
likely these days, the opacity issue alone will create a violation.

Note, this is not an issue for sheetfed presses using standard sheetfed
inks as those inks utilize a different drying mechanism other than the
application of heat. Also, those inks having a lower ink oil content,
typically about 24%, and an EPA-acknowledged substrate (paper) retention factor of

Jeff Adrian
The John Roberts Company
Minneapolis, MN

Debra Kramer wrote:
>This question was posted from the PNEAC web site. I will forward
>I was wondering if anyone had ever heard of opacity problems (excessive
>smoke) from a press dryer. The press is a 4 color web offset press. I
don't know the exact width but it doesn't appear to be any larger than 40 inches
across the web. I have several other small printers who have dryers on their
presses. I have never seen this problem before. If anyone has could you tell me
what was the source of the problem and what was in the smoke (was it made up of
primarily water vapor or VOCs)?



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