Printech Archives, August 1996: Modified method 24

Modified method 24

Tue, 06 Aug 1996 07:43:59 -0400

I do not know what the "modified" method 24 is yet either. Matt Kaarlela is
looking into what has been done in Texas. No "modified" method 24 for
cleaning solvents has been adopted or approved by EPA.

Since the discussion has to do with solvents, my guess is that what is
going on has to do with the difference between VOC content and VOC
emissions. There was a long discussion about this at the end of the first
day of the May printing CSI meeting. A question was raised by the two
people from MacDermid [Ted Stasiuk (sp?) and I do not remember the
other person's name right now] because they had a cleaner that contained
a very low vapor pressure organic compound. This organic compound
was a VOC (it was not on the list of negligibly reactive compounds), but
they did not believe that it volatilized in typical industrial use. They also
had some other problems with method 24 (e.g., the organic in the cleaner
formed a lower boiling azeotrope with the solvent that was used to spread
the sample in the sample dish in ASTM D-2369. This azeotrope came off in
the 1 hour, 110C bake. If a sample of cleaner without the spreading
solvent was put in the dish and baked there was much less weight loss.

I do not recall exactly who else took part in this discussion. I was there as
were Gary Jones, Dale Kalina and (I think) Jeff Adrian - there may have
been a few more people there as well. A recurring theme (raised in
response to the question) in this discussion was that there is a difference
between VOC content of a cleaner and the VOC emissions that occur
when a cleaner is used. The VOC content of a cleaner can be determined
by a test method. The test method might be all or part of method 24. In
many cases (e.g., if the cleaner is not a water-based cleaner it might be
easier just to assume that the cleaner is 100% VOC). The emissions that
ocur when a cleaner is used need to be determined by material balance.
For example, say toluene were used by a lithographer for blanket
washing. Toluene is 100% VOC, but the emissions from cleaning with
toluene would not be equal to the amount of toluene used since there
would be toluene left on the shop towels and in other cleaning wastes. To
get the exact amount of emissions you would need to subtract the toluene
on the towels and in the wastes from the toluene used. The difference
between usage and the result of the material balance would be smaller for
the most volatile cleaners and larger for the least volatile cleaners. Work
practices have an effect on the spread too (e.g., how the solvent is applied
to the towels or to the press parts being cleaned, covers on containers
holding used shop towels, etc.).

Rather than performing the material balance, I think that some people have
come up with the idea of "modifying" method 24 to take the place of the
material balance. I (personally) and we (EPA) do not think this is a good

Dave Salman



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