Printing and environmental sustainability
Ivana Bolanča Mirković, Igor Majnarić, Sandra Mustač 1, Zdenka Bolanča
University of Zagreb, Faculty of Graphic Arts
Getaldićeva 2, 10000 Zagreb, Croatia
E-mail: ivana.bolanca@grf.hr, igor.majnaric@grf.hr,zdenka.bolanca@grf.hr
1
Bsc student, University of Zagreb, Faculty of Graphic Arts
Getaldićeva 2, 10000 Zagreb, Croatia
E-mail:sandra.mustac@gmail.com
Abstract
The impact of the printing process on the environment is significant. This paper explores the
voltage of reverse roller in indirect electrophotography printing in the field of 0V to -250 V on
the life end of the printed products through the efficiency of recycling. In addition, the quality
of color reproduction is discussed. For the printing is used: uncoated woodfree paper, doublesided coated paper and Soho coated paper.
Characteristic of the results of image analysis handsheets made from recycled fibers prints
obtained by changing the voltage of reverse rollers from 0 to -200V is reduced in the total dirt
spot number and increasing in the dirt spot area. The efficiency of recycling is the highest for
printing on uncoated paper, then on Soho coated paper, and the worst on double-sided coated
paper. The quality of fullcolored prints observed through the volume gamut of prints gives
reverse results.
This is just part of a comprehensive study involving all six separate stages of
electrophotography printing synchronal performed. In this study the use of experimental
design and creation of statistical models in the direction of optimization process and
environmental sustainability follows.
Keywords: environmental sustainability, digital printing, voltage of reverse roller,
quality of prints, recycling
1. Introduction
The concept of environmental sustainability refers to the systematic conditions that should not
be disturbed by human activities either at a global or regional level more than the planet
allows. At the same time all the natural resources must not be depleted, and have to be
sufficient for the next generations. These two requirements should be in balance with the third
one regarding sustainability which refers to the principle of ethics and fairness.
Ecological flexibility is the capacity of an eco-system to overcome certain disruptions without
irreversible losses to conditions of its balance. Ecological space is the amount of energy,
resources and territory which can be used in environmentally sustainable way, and ecological
footprint points this out. Environmentally more sustainable product system and demands of
sustainable conditions will result in production and consumption that are in the system of
contemporarily industrial society and sustainability. The term of sustainability is significant
for the development, and it includes energy and material flows, closed loop systems, clean
technologies, economical and social factors, implementation of society values and quality.
Therefore, the switching to sustainability is large and complex process of technological, economical
and society innovation in which many differences have to adjust and find their place.
Environmental awareness, health and safety factor have an important role in identification of
printing technologies for the future. In order to increase effectiveness of resource usage and
effectiveness of environmental management system, life cycle assessment of the product has
to be considered and included in planning and projecting, starting from early stage of design.
The level of environmental awareness is present in printing industry, which enables making
the right choices. Significance of making the right choice is in the field of printing substrates
(substrates with high content of secondary raw material, substrates made from total chlorinefree process), inks (lower solvent content level biodegradable inks, formulation with more
renewable raw material), printing (clean technologies, preparation of printing forms with no
wastewater which contains chemicals from the process, cleaning agents for machine elements
which are based on renewable resource) and postpress finishing (binding process can be
specified to enable full recycling of paper content without glue contamination.
The main component of the waste is paper used in the preparation of the printing process. Due
to preparatory process for offset printing machine overall paper consumption is by 3.7 times higher
for smaller editions in relation to a digital offset printing machine [Kadam S.R., Evans M.E.,
Rothenberg S. 2009]. The offset printing inks are present with the amount of about 2.7g per
one print at smaller editions, and are decreased as the edition increases. The amount of ink
that goes to waste is less in digital offset printing than in conventional process.
Shown results are a part of an extensive research of the relevant factors in technological
process of digital electrophotography printing, simply defined by the terms of tamping,
exposure and developing. In this paper, the influence of changing the voltage of the reverse
rollers in relation to reproduction quality, and in relation to the last phase of the lifecycle and
properties of recycled fibers are discussed.
So far, the process of recycling is studied a lot. The domain of influential process factors is
being researched: the kind and the amount of chemicals used in various process stages, pH
values and fiber suspension consistency, temperature of suspension, the time of disintegration,
hydrodynamic flotation factors [Thender K., Pugh R.J.,2004; Zhao Y. et al. 2004; Azevedo
M.A.D. et al., 1999, Luo Q. 2003]. Machildon and co-authors and Magda have researched the
efficiency of the flotation in relation to size, shape and surface characteristics of dispersed
particles of printing dye, the volume of the air and the size of the air bubbles [Machildon L.
et. al. 1999; Magda J.J. 1999]. In the described issues the most of the studies were dedicated
to hydrodynamic factors of recycling process, the influence of chemical and physical system
conditions to the process efficiency, while the influence of printing techniques and graphic
materials were less studied [Carre B., Magnin L., 2004; Manning A., Fricker A., Thompson
R,. 2006; Bolanca Mirkovic I., Bolanca Z., 2005; Schiller A. 2008].
According to gained results the contribution of this paper is determining the influence of the
conditions in digital indirect printing based on electrophotography using liquid toner
ElectroInk on the quality of the prints and characteristics of recycled fibers, which presents
the contribution to determinants for further development within the meaning of sustainability
in that area.
2. Experimental
For the printing HP Indigo TurboStream machine based on indirect electrophotography is
used. The printing form contains following elements: standard CMYK RGB wedge in the
range from 10-100 screen value, textual positive and negative microelements, standard wedge
for production of ICC profile and 3D gamut, and standard ISO illustration for visual control.
The prints are made on paper with Soho coat for digital printing, both side coated and
uncoated paper for conventional offset printing. The bases of the papers have the same
chemical composition of the paper raw materials and the difference is in the coating.
After the calibration of the machine, the printing is followed, with the correction of the
voltage of reverse roller, for the next voltages: 0V, -50V, -125V, -200V and -250V.
Figure 1. Indirect electrophotography printing
Tamping of photoconductor is the initial phase of electrophotography process. The next phase
is exposing, which is carried out with the laser head which forms four light rays at once. The
third stage in the indirect electrophotography is developing. It is conducted in three separate
parts: the development with the processing drum, developing with reverse rollers and fixing
with squeegee roller. All these aforementioned distinct phases are performed synchronized
and they are the subject contented of our project, within which are researches presented in this
paper.
This is followed by spectrophotometric analysis made with X-Rite SwatchBook and
ColorShop 2,6 application. From ICC profile with the use of MONACO Platinum programe
the gamut of prints is established. In the paper the curve of reproduction, ΔE CIE Lab and 2D
and 3D gamut of the reproduction are shown.
Figure 2. Workflow
For recycling of the prints alkaline chemical deinking flotation is used. In the process the next
chemicals are used: sodium hydroxide 1%, hydrogen peroxide 1%, sodium silicate 2%, DTPA
0,2%, and surface active substance 0,4%. Consistency of the suspension in the phase of
disintegration is 10%, while in the flotation phase the consistency is 0,6%. The time of the
disintegration is 10 minutes, and the time of the flotation is 8 minutes [Bolanča Mirkovic I.,
Bolanča Z. 2005].
After the disintegration and flotation laboratory handsheets are made with the use of standard
sheet former Rapid- Köthen, according to INGEDE Method 1 and ISO 5269-2[ ISO 5269_2].
On this laboratory handsheets using spectrophotometer Technidyne Color Touch 2 model
ISO, before and after flotation brightness [ISO 2470] and effective residual ink concentration
are measured [TAPPI T 567 pm-97].
According to the recycling process phases image analysis is made with the use of SpecScan®
Apogee System software in accordance with TAPPI standard method [TAPPI T 563 pm-97]
3. Results and discussion
Figure 3 shows the results of image analysis from handsheets made of fibers from different
phases of recycling prints obtained by varying the voltage of reverse rollers in indirect
electrophotography printing with HP Indigo TurboStream.
a) Sample for the recycling on double sided
coated paper
b) Sample for the recycling on Soho
coated paper
c) Sample for the recycling on uncoated paper
Figure 3. Total dirt spot count versus voltage of reverse rollers and types of the printing
substrate
The common characteristic found in results is the reduced of total dirt spot number by
variation of voltage reverse rollers from 0 V to -200 V. The results are dependent on the
substrate characteristics. In used printing substrates there is no difference in the chemical
composition of the raw paper, but in the finishing process in relation to the coating. For
double-sided coated paper prints, standard for offset printing, efficiency of the deinking
flotation procedure ranges from 10-26% depending on the voltage of reverse rollers in the
recycling samples printing process. Slightly higher recycling efficiency (33-47%) is achieved
by using the paper with Soho coating which is specially adjusted for indirect
electrophotographic printing. The best efficiency of recycling (75-84%) is achieved by using
woodless uncoated offset paper.
The coating of paper is a significant factor of the recycling process effectiveness. The fact
must be acknowledged that the coating process assists in dispersing the fillers in the coating.
In recycling process dispersants are at time surface active and together with alkali can lead to
acceptable ink detachment from the coated paper. These species can hydrophilise ink
containing agglomerates and hinder flotation efficiency as well as contribute to unwanted
foam generation and/or stability.
The coating of paper is a significant factor of the recycling process effectiveness. The fact
must be acknowledged that the coating process assists in dispersing the fillers in the coating.
In a recycling process at time, dispersants are surface active and together with alkali can lead
to acceptable ink detachment from the coated paper. On uncoated paper the adhesion of
printing ink to paper depends on paper properties such as surface structure, fibre type, ash
content and drying mechanism of the chosen printing process.
These species can hydrophilise ink containing agglomerates and hinder flotation efficiency as
well as contribute to unwanted foam generation and stability. On the uncoated paper, the
adhesion of printing ink to paper depends on paper properties such as surface structure, fiber
type, ash content and drying mechanism of the chosen printing process.
The results show the opposite relationship between the voltage of reverse rollers in indirect
electrophotographic printing of samples for recycling and dirt spot area (Fig. 4)
a) Sample for recycling on double sided coated
paper
b) Sample for the recycling on Soho
coated paper
c) Sample for the recycling on uncoated paper
Figure 4. Total dirt spot area versus voltage of reverse rollers and printing substrate types
With increasing of the negative voltage of reverse rollers in the printing, the total dirt spot
area on the handsheets made from recycled fibers is increased. In this case the impact of the
printing substrate on recycling is also proven. Thus, recycling of prints made with the -250V
voltage of reverse rollers, efficiency to reduce dirt spot area of the substrate with a Soho
coating is 48%, for the surface with double-sided coating designed for offset printing is 75%
and for uncoated woodfree paper is about 90%. Reduce of total dirt spot number with increase
of total dirt spot area indicates the increase in the size of individual particles. For better
monitoring and interpretation of the deinking flotation mechanism, Figure 5 shows the dirt
spot histograms for dirt spot size from 0001-0006 to >=5 mm2.
After flotation
a) Sample for recycling on double sided coated paper
Before flotation
Before flotation
b) Sample for the recycling on Soho coated paper
After flotation
After flotation
c) Sample for the recycling on uncoated paper
Before flotation
Figure 5. Dirt content histograms for handsheets made from recycled print fibers with the
reverse rollers voltage of -200V
The research results show that the larger negative voltage of the reverse roller formed larger flat dirt
spot areas, sometimes larger than 5 mm2. Handsheets made from the fibers after the disintegration of
prints on uncoated woodfree paper have the greatest number of such spots (141-199) depending on the
voltage of the transmission drum, while such spots can be at least expected if the double-sided coated
paper prints are used for recycling. On the prints made on woodfree uncoated paper and Soho coated
paper the efficiency of recycling process in comparing the total dirt spot area in the total of >= 0.04
mm2, and the total of <0.04 mm2 is almost equal. For prints on uncoated woodfree paper recycling
efficiency is around 90%, while for the prints on Soho coated paper efficiency is about 42%.
Recycling specifics of prints in the described experimental conditions are significant for prints on the
double-sided coated paper for offset printing, referring to the good efficiency of about 82% for the
recycling when it comes to spots in the 0.04 - >= 5.000 mm2 for prints made at reverse roller voltage
of -200 V and a very inefficient flotation efficiency for spots in the class size of 0.001-0.04 mm2
should be pointed out. Given that this is the efficiency of removing the spots below 1%, this is
probably due to fragmentation of large particles and the inability of flotation methods for their
removal as well.
Results of image analysis are further tracked and verified through the measurement of
effective residual ink concentration and brightness. The highest brightness have handsheets
made from recycled fibers prints on Soho coated paper (Brightness102) and the value is
slightly increased by increasing the negative voltage values of the transfer roller in printing
the recycling samples. Handsheets made from recycled fibers of prints on double-sided coated
paper have a slightly lower brightness (brightness around 85) which is almost changed
compared to the voltage of recycling samples. Effective residual ink concentration decreases
for handsheets after flotation in comparison to those before flotation. Correlation between
effective residual ink concentration and brightness is determined.
Given that the purpose of this paper is establishing links between the end of life of the printed
product, the quality of prints with the ultimate goal of process optimization in the domain of
suitable environment is shown below. As indicators of reproduction quality of a certain stage
in the process of indirect electrophotography process, two dimensional and three-dimensional
reproduction Gamut are shown.
Print on uncoated paper
Print on double sided coated paper
Print on Soho coated paper
Figure 6. Gamut of print, obtained by using the voltage of reverse roller of 0 V, -125 V and - 250 V on
Soho coated paper
Table 1 Volumes of gamut V CIE L * a * b * CCU
Sample
Uncoated paper
Double-sided coated paper
Soho coated paper
Voltage 0
382.434
551.702
424.572
Voltage -125 V
517.113
730.174
581.387
Voltage -250 V
546.834
762.139
618.448
The largest reproduction gamut is achieved at a voltage of the reverse rollers - 250 V on the
double-sided coated substrate. For this substrate is specific that the central part of gamut body
at a voltage of 0 V has the best reproduction of green and blue tones. Increasing the voltage
leads to a smaller reduction in reproduction of blue, and increase in the reproduction of
magenta, red, yellow and green. In relation to the research, the minimum reproduction gamut
is achieved at uncoated substrate, In the typical cross-sections there is a change in magenta,
red, yellow and light green, increasing the voltage from 0V to -125 V. Voltage from -250V
causes the change in tones containing a higher percentage of the yellow.
Gamuts obtained by reproduction on Soho coated paper are very similar in characteristic
cross- sections to those on uncoated paper. The difference is noticed in light and dark shades,
because the ink is better accepted on Soho coated surface.
4.
Conclusion
Based on the results of image analysis a reduction in total dirt spot number and increasing the
dirt spot area for voltage change of reverse rollers from 0 to -250 V for indirect
electrophotography on recycled print samples is proven. This general trend show prints on all
used substrates.
Flotation deinking efficiency is dependent on the voltage of reverse rollers (0V-250V) in
indirect electrophotography printing of samples and on the characteristics of the substrate as
follows: double-sided coated paper 10-26%, Soho coated paper 33-47% and uncoated
woodfree paper 75-84%.
The largest brightness have handsheets made from recycled fibers of prints on Soho coated
paper. The research results in the context of reproduction quality indicators of the observed
phase of indirect electrophotography process are as follows: the largest gamut is realized with
printing on double-sided coated paper, followed by reproduction gamut on the Soho coated
paper and the smallest gamut is achieved with reproduction on uncoated paper.
Given that the indirect electrophotography printing is complex process, with six separate,
synchronous phases, the needs and characteristics of graphic material, along with a number of
factors in the field of chemical deinking flotation (if the life end of printed products is
followed) should be considered. In the further research experimental design will be used and
statistical models will be created to obtain information about optimizing in the direction of
environmental sustainability in this area.
5.
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
Azevedo M.A.D., Drelich J., Miller J.D.,(1999) The effect of pH on pulping and flotation of mixed
office wastepaper, J.Pulp Pap. Sci. 25(9):317(1999),66-72
Bolanaca Mirkovic I., Bolanca Z., (2005), Optical properties of deinked pulp, Journal of Imaging
Science and Technology, 49(3)(2005)284-292
Carre B., Magnin L. (2004) Digital prints: A survey oft he various deinkability behaviours, 7 th Research
Forum on Recycling PAPTAC-TAPPI, Quibec Canada
Carre B., Magnin L., Galland G., Vernac Y., (2003), Printing process and Deinkability, Das Papier, 12
(2003) 41-45
ISO 2470, Paper, bord and pulps- Measurement of diffuse blue reflectance factor (ISO brightness)1999
ISO 5269-2 Pulp-Preparation of laboratory sheets for physical testing, Part 2. Rapid Köthern method
Kadam S.R., Evens M.E., Rothenberg S., (2009) A comparative study of the environmental aspects of
litographic and digital printing processes, GATF, Rochester
Luo Q., Deng Y., Zhn j., Shin WT., (2003), Foam Control Using a Foaming agent Spray: A Novel
Concept for Flotation Deinking of Waste paper, Ind. Eng. Chem. Res. 42. 3578-3583
Machildon, M., Lapointe, B., Chabot, L.,(1999) The influence of particulate size in flotation deinking of
newsprint, Pulp Pap. Can. 90(4):90(1
Magda J.J., Lee J.Y.,(1999), A critical examination of the role of ink surfacehydrophobicity i flotation
deinking, Tappi J., 82(3): 97(1999),139-145
Manning A., Fricker A., Thompson R., (2006) Deinking of Indigo prints using high-intesy ultrasound,
Surface Coatings International 89B2
Schiller A. (2008) Deinkability of UV prints into ink formulation, Final COST Conference, Bordeaux
TAPPI T 563 pm-97, Equivalent Black Area (EBA) and count of visible dirt in pulp, paper and
paperboard by image analysis
TAPPI T 567 pm-97, Determination of effective residual ink concentration by infrared reflectance
measurement
Theander K., Pugh R.J.,(2004), Surface chemicals concepts of flotation deinking, Colloids and
Surfaces A: Physicochem. Eng. Aspects 240 (2004
Zhao Y., Deng Y., Zhu J.Y., Progress in Paper Recycling 14(1):41(2004).