Impressions - September 2020 - 43

Solid Waste
Plastisol ink is essentially 100% solids and often can be disposed
of as a plastic solid. Simply spread residual ink on a piece of
cardboard and run it through the dryer a few times until it is
completely cured. At that point, you may be able to dispose of
it as regular plastic waste.
Larger amounts either can be recycled for other uses or cured
to form a solid. Once cured, you also may be able to dispose
of it as regular plastic.
This method also can be used for most water-based inks, but
running it through a dryer may not be necessary. Simply letting
it air-dry or allowing the liquid to evaporate should suffice.
Some high-solids water-based inks do need to be cured in the
dryer, as they won't air-dry.
Remember, it's important to confirm with your local
regulatory authority what is deemed acceptable before you dispose
of plastic solids as regular waste.This is as simple as it gets. But
what about the leftovers from the screen-cleaning or reclaiming
process? That's where things get muddy - no pun intended.
Residual Waste
The next step in the cleaning process is to remove ink from
screens and the various tools used, including squeegees, spatulas,
stirring sticks and more. In this step, the ink typically is cleaned
using solvents or other cleaning liquids.That resulting sludge
should never be flushed down the drain.
Instead, it should be collected in a separate tank or container
and, when full, disposed of properly.There are many commercial
companies, such as Safety Kleen, that can handle this disposal,
as long as the inks and chemicals you use don't contain any
restricted chemicals, such as heavy metals (lead, cadmium, etc.).
The company you choose may require a sample to be analyzed
for assurances.
The approved sludge that the waste company takes away then

can be incinerated. Some of the waste may be used as fuel to
heat and create asphalt or cement. Some of the resulting ash
also can be blended into asphalt.
Waste Water
When washing off ink residue with water during the cleaning
or reclaiming process, there are certain protocols that must
be obeyed. Particularly, it's important to prevent inadvertent
residue and waste from going down the drain. This protocol
should be implemented regardless of whether water-based or
plastisol inks are used, and also should include emulsion, cleaning,
reclaiming, adhesives and other chemical waste.
Many shops use commercial industry waste-disposal
services, along with in-house clarifying or chemical-recirculating
systems, to responsibly deal with waste water. Clarifiers are settling
tanks that are used to remove solid particulates or suspended
solids from liquids. Some larger clarifying tanks may have a
pre-filtering unit, which will remove large particles before the
water goes into the tank. After being washed down the drain,
the clarifier allows time for pigment, emulsion or other solids
particles to settle at the bottom of the tank.
If your shop doesn't use much water, the clarifier could be
as small as 10 gallons. Larger shops may need one or multiple
tanks holding thousands of gallons each to give the suspended
particles time to drop to the bottom.The sludge that collects
at the bottom will be removed for disposal later by your wastedisposal service.The remaining clear water on top can be reused
or passed down the line to your city's water-treatment facility.
A chemical-recirculating system works like a mini clarifier,
except it reuses chemicals instead of water.Typically, this system
can be set up as a cleaning station where the screens and tools
are washed with a chemical.The waste liquid is collected beneath the wash station and clarified.The clear chemical on top
then gets syphoned off and reused. Such a system can reduce
chemical use and save costs.
The amount of residue a shop generates can vary, depending on how well
inks are removed from the screens and
tools prior to washing. Keep in mind that
anything going down the drain must be
dealt with at some point.The better you
are at pre-cleaning inks off the screens,
the more positive the impact will be on
our planet. Overall, the screen-printing
industry can minimize negative environmental effects by diligently and properly
disposing of waste. 
Kieth Stevens is the Western regional sales manager
for International Coatings. He has been screen
printing for more than 42 years and teaching
screen printing for more than 12 years; is a regular
contributor to International Coatings' blogs; and
won SGIA's 2014 Golden Image Award. He can be
reached at kstevens@iccink.com. For more information, visit iccink.com and read the company's
blog at internationalcoatingsblog.com.

This diagram shows how
water-clarifying systems work.
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Impressions - September 2020

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