EPA744-F-01-001
February 2001
ur
Design for the Environment
Gravure Partnership
The Effect of Ink Temperature
On Solvent Losses and Print Quality
GAA
WESTERN
MICHIGAN
UNIVERSITY
U.S. EPA
Background—The U.S. Environmental
Protection Agency's (EPA) Design for the
Environment (DIE) Program, the University of
Tennessee (UT) Center for Clean Products
and Clean Technologies, and Western
Michigan University (WMU) partnered with
the Gravure Association of America (GAA),
gravure printers from the packaging and prod-
uct sectors, and other industry experts to iden-
tify 1) common environmental issues for
gravure printers, especially small- and medi-
um-sized businesses in the packaging and
product sectors; and 2) potential risk reduction
and pollution prevention opportunities for
addressing key issues.
Packaging and product gravure printers are
particularly concerned about solvent losses
from ink during press operations—including
solvent losses from the ink sump and ink pan
areas—which might be reduced by controlling
ink temperatures. Smaller gravure printing
operations generally use a press-side sump to
pump ink to the press, where the ink may
absorb heat from
U.S. Gravure Industry Statistics
Sector
Publication*
Packaging
Product
Total
Avg. employees
Annual sales ($/
#of plants
24
276
174
480
per plant**
'yr)**
Avg. presses
per plant
6.3
2.5
2.8
2.8
<20
>$18 billion
Data from 1987-1993 (GAA Profile Survey of the U.S. Gravure
Industry).
* 2000 data from GAA.
"Data for publication, packaging and product combined.
the ambient air or
from press opera-
tions. Large publi-
cation printers
generally have in-
line heat exchang-
ers and closed-
loop ink delivery
systems, which are
not as subject to
solvent losses from
elevated ink tem-
peratures. The
Gravure Partner-
ship performed a
preliminary study
of the effect of ink
temperature on solvent losses and print quality,
which is summarized below. The results sug-
gest that packaging and product printers could
reduce solvent losses, and, in some cases,
improve print quality by controlling ink tem-
peratures. Further study by the industry is
needed to confirm these results.
Gravure Industry Statistics—The gravure
industry comprises three main sectors: publica-
tion, packaging, and product printing.
Publication gravure plants are generally large
operations that tend to be more automated,
with more advanced systems for addressing
environmental concerns. Packaging and prod-
uct gravure plants are often small- to medium-
sized printing facilities with fewer employees,
fewer presses, and more limited resources.
Risk Reduction Opportunities—The partner-
ship began with a scoping phase to identify
potential opportunities for packaging and
product printers to reduce emissions and risk
from printing operations. Project partners con-
sulted with GAA and industry experts to
develop a preliminary list of risk reduction
opportunities (see box, page 2), which were
then verified through site visits to gravure
printers in the packaging and product sectors.
DfE project leaders chose to study the effect of
ink temperature on VOC emissions and print-
ability for the following reasons:
• Ink temperature's effect on solvent losses
and print quality are common problems
among various packaging and product
printers, in spite of different inks, number
of colors, and substrate.
• By controlling ink temperature, printers
might gain print quality and cost benefits
as well as environmental benefits.
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Emissions from the ink sump and ink pan areas are
not always captured by air pollution control equip-
ment attached to presses.
Reduction in the use of hazardous air pollutants
(HAPs) and VOCs could reduce adverse impacts on
human health and the environment (due to direct tox-
icity from HAPs and indirect effects of smog forma-
tion from VOCs).
Risk Reduction Opportunities
Risk reduction opportunities identified by the DfE
Gravure Partnership include:
• Volatile organic compound (VOQ/solvent emis-
sions reduction
- from floor cleaning
- from press operations
• Hazardous waste generation
• Shop towel management
WMU Temperature Control Study
The WMU laboratory experiment met key objec-
tives of the DfE Gravure Partnership by:
• Developing information on the effects of ink
temperature on solvent consumption and print
quality.
• Determining that technologies to moderate or
control ink temperatures are a worthy subject
for further investigation by the industry.
Study Parameters
Controlled conditions
Press size:
Press speed:
Substrate:
Run length:
Ink type:
Solvent blend:
Initial ink vol.:
42" wide, 4-color press
300 ft/min
1.25 mil polyethylene film
3-hour production run
(samples taken every 20
minutes)
Type C (nitrocellulose),
magenta and cyan
50% n-propyl acetate,
50% n-propyl alcohol (by
volume)
60 Ib (solvent + ink)
Variable conditions
(average ink temperature)
66°F (cooled with cold water and ice)
79°F (ambient)
92°F (heated with hot water)
Measurements taken
Viscosity (adjusted every 5 minutes)
Solvent consumption
Ink consumption
Printability
• Optical density
• Gloss
• Microstructure image analysis (dot
structure)
• Tonal response
• Rub resistance (Sutherland Ink Rub
Tester)
Gravure Partnership Purpose—The purpose of the DfE
Gravure Partnership was to 1) identify risk reduction and
pollution prevention opportunities for addressing key envi-
ronmental challenges in the gravure industry, 2) determine
whether promising risk reduction techniques might also
have cost and/or performance benefits, and 3) provide the
risk, performance, and cost data to the gravure industry for
further technology verification.
Following scoping, a laboratory experiment was con-
ducted at WMU's Printing Pilot Plant to explore the rela-
tionships between ink temperatures, solvent losses, and
print quality (Sosa, 1999). The results of the WMU tem-
perature control study, presented here, provide preliminary
information to the industry on the potential risk, perform-
ance, and cost benefits of ink temperature controls.
Temperature Control Study
Purpose
The purpose of the preliminary laboratory study was to
evaluate the effects of temperature on solvent consumption
and print quality.
Method
Two colors of nitrocellulose (Type C) ink common to
packaging printers were used in 3-hour production runs on
a 42", 4-color gravure press at 300 ft/min. Type C inks are
generally ester or ketone inks. The solvent blend used in
the temperature experiment was 50% normal propyl
acetate and 50% normal propyl alcohol (by volume).
Samples were taken for the two inks at three different ink
temperatures: 66°F, 79°F, and 92°F.
The cooler temperature was obtained by
using cold water and ice to cool water
circulating through copper coils sub-
merged in the ink sump. The warmer
temperature was obtained by circulating
hot tap water through the copper coils.
No temperature controls were used for
the middle (ambient) temperature,
which increased by 3°F to 5°F during
the course of the 3-hour run.
During the runs, ink temperature
was measured and viscosity was tested
and adjusted every 5 minutes. Print
quality measurements were taken every
20 minutes. Several measures of print-
ability were obtained. (See Study
Parameters Box.)
Gravure Partnership
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Solvent and Ink Consumption Results
Colder ink needs more solvent to bring it to target
viscosity, but as temperature rises, the solvents in sol-
vent-based inks evaporate faster and require more sol-
vent to maintain viscosity (Sosa, 1999).
• Total solvent consumption (solvent added during
makeready plus solvent added during the print run)
in the magenta ink increased with increasing tem-
perature (see Figure 1).
• Total solvent consumption in the cyan ink was slight-
ly greater at 66°F than 79°F due to the amount of
solvent needed to reach target viscosity during make-
ready Solvent consumption increased from 79°F to
92°F (see Figure 1).
• Total mass (ink plus solvent) consumption
increased with increasing temperature: 9%-28%
increase from 66°F to 79°F and 37%-56% increase
from 79°F to 92°F.
• Ink use (not including solvent added during make-
ready or the trial) also increased as temperature rose
(see Figure 2). The increase in ink consumption at
higher temperatures may be due to the higher pig-
ment to solvent ratio of warmer ink, which prints a
thicker layer.
Print Quality Results
In the WMU study, printability and quality were
affected as ink temperature increased, with both print-
ed solids and tones affected (Sosa, 1999).
• Reflection Density—dropped by 0.055% of reflected
light for every 5°F temperature increase from 79°F
to 92°F (see Figure 3). Theoretically, ink at higher
temperatures should print darker colors, but
reduced reflection densities at higher ink temper-
atures have been reported elsewhere (Celio, 1998).
Warmer inks evaporate faster, which can cause a
wettability problem and screening. Screening is a
print defect caused by uneven flow of inks between
cells (GAA, 1991). In the WMU study, as ink tem-
perature rose to 92°F the ink dried before spread-
ing adequately on the substrate, thus reducing the
overall printed solid area and the reflection density
(Sosa, 1999). Printed tone steps were most affected;
the finest dots did not print at all.
• Specular gloss—decreased by 20% from 66°F to
79°F, but increased by 3% from 79°F to 92°F (see
Figure 4). Colder ink requires more solvent to reach
target viscosity; lower pigment concentration leads
to a thinner printed ink film. In the WMU study,
the specular gloss measurements for the colder ink
Total Solvent Consumption
12
Figure 1
o
Vj
Q.
Magenta
Cyan
- 3.5
79°F
Ink Temperature
92°F
Ink Consumption
Figure 2
o
c_3
7.E
Magenta
Cyan
4.5
Print Quality
2.1
2.0
1.9
1.8
1.7
1.6
1.5
en
cc
66°F 79°F
Ink Temperature
Reflection Density
2.05
92°F
Figure 3
79°F
Ink Temperature
92°F
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were influenced by the glossy polyethylene
substrate showing through the thinner ink
film. The increase in specular gloss seen
from 79°F to 92°F may be due to the
decreased wettability and increased screen-
ing observed at higher temperatures.
Screening may have caused more light to be
reflected from the polyethylene substrate.
Dot structure (see Figures 5 and 6)—hot
inks had deformed dot structure caused by
the "donut effect." As ink fills the engraved
cells of a printing cylinder, it forms a con-
cave shape leaving an air bubble to be
trapped between the ink and the substrate.
The air prevents the ink from being trans-
ferred to the middle of the printed dot and
forces the ink to be spread outward, creating
a "donut." Warmer, less viscous ink pro-
duces a bigger concave meniscus as it lies in
the cylinder cells, which results in more air
being trapped and a larger donut. As the
donut effect increases with temperature, the
amount of printed image decreases and the
printed dot becomes bigger (Sosa, 1999).
Deformed dots caused by the donut effect
also had bigger perimeters. As the dot
perimeter increases so do the dot gain and
mottle, causing a decrease in print quality.
Finally, photographs taken in the solids
areas confirmed the reduced wettability of
the hotter ink; the white, non-printed areas
of the solids rose with increasing ink tem-
perature.
Haze—not a quantifiable variable in the
WMU study, but appeared to increase with
decreasing temperature. Decreasing efflux
time and/or doctor blade pressure may
reduce haze.
Rub resistance—no change in rub resistance
at different temperatures. A Sutherland ink
rub tester was used to rub the printed films
against a white surface for a specific amount
of time. The reflection density of the white
surface was measured before and after the
test to determine the amount of ink trans-
ferred from the printed film to the surface.
The difference in the reflection densities of
the hottest temperature and the coldest tem-
perature inks were within the resolution of
the densitometer.
Print Quality — Specular Gloss
80 f _73.5
70
60
_ 50
^o
I 4°
^ 30
_ro
§ 20
% 10
Figure 4
Cyan
79°F
Ink Temperature
92°F
Magenta elongated tone (25%)
— 150 lines per inch
Figure 5
y 9 9
* * • *
**••*
79°F
Cyan compressed tone (25%)
— 150 lines per inch
« • *
79°F
Magenta solid —150 lines per inch
92°F
Figure 6
« V <
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Conclusions
The WMU study assessed the effects of
three ink temperatures (66°F, 79°F, and
92°F) on solvent consumption and print
quality of Type C inks under laboratory-con-
trolled conditions. The study was designed to
provide preliminary data on the potential
benefits of ink temperature controls to the
gravure industry for further technology verifi-
cation (see box on Study Limitations). The
results are promising.
• Small- and medium-sized printers in the
product and packaging sector may be able
to reduce solvent consumption, improve
print quality, and achieve cost reductions
by implementing ink temperature con-
trols.
• Decreasing solvent consumption and sol-
vent emissions could also reduce health
risks because of reductions in potential
exposures to workers or the public.
• The greatest benefits may occur when ink
temperature is maintained near a typical
room temperature rather than chilled to
below typical room temperatures, suggest-
ing less chilling is needed to achieve opti-
mal results.
Study Limitations
• The WMU laboratory study was designed to evaluate the potential risk, perform-
ance, and cost benefits of ink temperature controls for gravure printers. The
study does not establish a definitive relationship between ink temperature, sol-
vent emissions, and print quality.
• The study evaluated the effects of ink temperature on Type C inks only. Results
may differ with other ink types.
• The range of test temperatures (66°F to 92°F) was selected to represent the
extreme of printing conditions that might be encountered in the industry. Smaller
printers may have ink temperatures approaching the upper limit in the summer
months, but these higher temperatures are not typical of year-round operating
practices.
• Many ink and solvent systems used in packaging and product gravure have an
affinity for pressroom air moisture, particularly at low temperatures. Moisture
pickup due to low ink temperature can cause blushing and ink kick-out. The
study did not directly assess the moisture pickup of the colder inks, but no blush-
ing and ink kick-out effects were seen.
Potential Cost Savings
Parameter
Solvent emissions (Ib/yr)
Ink consumption (Ib/yr)
Annual solvent costs
Annual ink costs
Scenario 1
113,400
97,200
$56,700
$388,800
Scenario 2
86,400
86,400
$43,200
$345,600
Reductions
or savings
27,000
10,800
$13,500
$43,200
Solvent & ink costs
$445,500
$388,800
$56,700
• Ink temperature controls might also reduce
overall ink consumption (up to 20%-30%)
without adversely affecting print quality, but these
results need to be confirmed on different substrates
and in "real world" settings.
• Ink temperature controls can also be expected to
reduce solvent use (perhaps up to 50%), especially in
the summer months when ambient temperatures are
higher.
Potential Cost Savings—Potential savings were estimat-
ed for two scenarios using the assumptions of the model
facility (see box at right) and the solvent and ink con-
sumption results from the WMU study. Scenario 1
assumes a small printer operates at 92°F for three
months and 79°F for nine months a year. Scenario 2
assumes the printer implements temperature controls to
maintain a constant temperature of 79°F all year.
Conditions will vary greatly by facility; many other
factors may also affect these estimates. Nonetheless, they
provide a starting point for companies to estimate their
Example Model Facility
Press size: 23" wide
Printing units: 3
Annual operation time: 7200 hr/yr
Press speed: 300 ft/min
Solvent use rate: 9 Ib/hr at 92°F
(per color): 4 Ib/hr at 79°F
Ink use rate: 6 Ib/hr at 92°F
(per color): 4 Ib/hr at 79°F
Solvent cost: $0.50/lb
Ink cost: $4.00/lb
own potential savings. Although these estimates do not
account for the cost of cooling, any cooling solution and
associated energy requirements that cost less than the
estimated savings above could result in payback after the
first year.
Industry Challenge—The results of the DfE Gravure
Partnership suggest ink temperature controls may present
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gravure printers with an excellent opportunity to prevent
pollution at the source, while improving print quality
and reducing costs. Small- and medium-sized printers
that experience printing inefficiencies due to fluctuations
in ink temperatures may benefit most from ink tempera-
ture controls, but no clear or commonly implemented
solutions for addressing these inefficiencies yet exist. The
DfE Gravure Partnership challenges the industry to con-
firm project findings to optimize printing operations. To
meet this challenge, gravure printers could:
• Independently evaluate the effects of ink temperature
on solvent and ink consumption, print quality and
cost.
• Assess and/or optimize current ink temperature con-
trol options, including
- Submerged copper coils in the ink sump, including
the cost and pollution implications of frequent
cleaning.
- In-line heat exchangers on the supply line.
- Room temperature control (air conditioning).
• Adapt a temperature control option from another
industry.
• Develop a new, innovative method for controlling ink
temperatures.
Questions to consider when evaluating the use of
temperature control in a printing facility include:
• How will less solvent consumption affect treatment
systems such as oxidizers and recovery systems?
• What is the cost of adding temperature controls on
press and providing cooling water?
• How do different colors and ink types behave, noting
that in this study the two Type C inks behaved differ-
ently?
References
Celio, Tino (1998). Ink Temperature Control in Gravure
Printing. Ambril, Swtizerland: Paper presented at the
annual meeting of the Gravure Association of
America conference, Memphis, TN.
GAA (1991). Tone Reproduction. Gravure, Rochester, NY.
Sosa, Rodrigo (1999). Effects of Temperature Control on
Gravure Packaging Ink: A Thesis Submitted to the
Faculty of the Graduate College in partial fulfillment
of the requirements for the Degree of Paper and
Imaging Science, Western Michigan University,
Kalamazoo, MI.
What is EPA's Design for the Environment
Program?
EPA's Design for the Environment (DfE) Program partners with stake-
holders to help businesses help the environment. DfE projects help
businesses design products, processes, and management systems
that are cost-effective, cleaner, and safer for workers and the public.
The DfE goals are to:
• Encourage businesses to incorporate environmental information
into their decision criteria.
• Effect behavior change to facilitate continuous environmental
improvement.
To accomplish these goals, DfE and its partners use several
approaches including cleaner technology and life-cycle assessments,
environmental management systems, formulation improvement, best
practices, and green supply chain initiatives.
To date, the DfE Program has brought environmental leadership to
over 2 million workers at over 170,000 facilities. Small- and medi-
um-sized businesses recognize DfE as a unique source of reliable
environmental (as well as performance and cost) information that
allows them to make better decisions.
How Can I Get More Information?
To learn more about EPA's DfE Program or the Gravure Partnership,
contact:
EPA's DfE Program
Phone:202-260-1678
Web site: www. epa.gov/dfe
The Gravure Association of America
Phone:716-436-2150
Fax:716-436-7689
UT Center for Clean Products and Clean Technologies
Phone: 865-974-9526
E-mail: socolofml@utk.edu
Rodrigo Sosa, RJR Packaging (formerly of WMU)
Phone:336-741-4974
E-mail: sosar@rjrt.com
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