Printech Archives, May, 1997: Re: Low-VOC, fast-drying blanket wash

Re: Low-VOC, fast-drying blanket wash

Jeff Adrian (
jeffadrian@johnroberts.com)
1 May 1997 07:28:10 -0500


Wayne & Angelina Zappia:

I am not aware of any "quick-drying" low-VOC blanket washes as those qualities
seem to be mutually exclusive of each other (quick drying & low-VOC). Perhaps
a better approach would be to rethink your requirements for cleaning with less
VOC emissions! That was the approach we took at John Roberts Company with
great success.

One often held belief is that the blanket must be completely dry before
restarting the press. We found that this is a myth. We examined how we were
cleaning a press, specifically the press blankets, and the need for quick
cleaning during the run (as contrasted to cleaning between runs). Here's what
we did.

We changed the method of cleaning blankets. We used a low vapor-pressure
cleaning solvent blend (v.p. less than 4). On the first turn of the cylinder,
we used the press wash to remove most of the ink onto a double padded shop
towel. One the second turn of the cylinder, a separate doble padded shop towel
that had been dipped in water and wrung out was used to remove the remaining
ink (very little) and the paper clays and dust. The cleaned blanket had just a
tiny bit of moisture remaining (looks like the side walls of your car's tires
just after washing). This remaining moisture is no problem as it is pulled of
on the first few sheets through the press on startup.

Note that with any slightly more oily solvent blend, be it low-VOC or low
vapor pressure, a little additional care is need to be certain the solvent
doesn't accumulate in the blanket gap, where upon startup, centrifigal force
would lead to "speckle-tone" thirty sheets in (NOT GOOD). Also, note that when
the first wiper is soiled with ink and is placed in the collection container,
the second "water wipe" can be rotated to the first ink wipe, and a new second
water wipe is started. By using wiper rotation, there should be no significant
increase in the number of shop towels being used. Actual time to clean the
blanket was not increased in any significant way. Try it.

Results: Our experience shows that each time we reduced the vapor pressure of
our solvent blends (originally at v.p. of 105), we cut purchases of solvent by
a third, and we doubled spent solvent recovery (with our centrifuge). This
recovery is important (we recycle the spent solvent) because if the solvent is
"in the drum" (even if your facility doesn't recycle the spent solvent), then
it cannot be considered an air emission. Your waste manifests will document
this fact.

I hope this provides you with some alternative ideas on VOC control. I have
some specific suggestions on how to effectively change "work practices" that I
would be happy to share with you if they would be useful to making a smooth
transition to low vapor pressure cleaning solvents.

Regards,
Jeff Adrian
The John Roberts Company

------- Forwarded Message Follows -------

I was wondering if anyone has had success with a quick-drying low VOC
(less than 4 lb/gal) blanket wash (for a large offset lithographic
Polychrome press, specifically) and could recommend a vendor. The
facility has tried Ecolo-Clean 35 (Varn) but found that it takes too
long to dry and is fairly labor-intensive.
Thanks.

--Angelina Zappia


 

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