Advanced technologies
2(1) (2013), 26-32
THE POSSIBILITY OF USING RECYCLED PAPER IN DIGITAL PRINTING
Ivana Jurič*, Dragoljub Novaković, Igor Karlović, Ivana Tomić
Faculty of Technical Sciences, Department of Graphic Engineering and Design, University of Novi Sad,
Novi Sad, Serbia
The demand for the use of recycled paper has increased recently. The original
motivation for paper recycling was primarily economic. The intention was to
use collected waste paper in the paper manufacturing. This was primarily the
concern in the countries without indigenous forests, which could ensure their
production of newsprint and packaging material. Today environmental concerns are the main motivation.
The main aim of the present research was to examine whether the papers
made of 100 % waste paper could replace the papers made of virgin fibers as
substrates in different digital technologies for monochrome prints. We chose
three digital printing machines that are based on different marking engine. Xerox DocuColour252 and RICOH MP7500 are based on electrophotography and
Canon IP4800 is based on ink jet. The line quality (edge raggedness), text
readability, print sharpness and print contrast on the prints were determined
by using the image analysis method. The results obtained for the print quality
on the recycled papers were very promising. Prints on the recycled papers
achieved a similar, and in some cases identical print quality as the prints on the
papers made with virgin fibers.
(ORIGINAL SCIENTIFIC PAPER)
UDC 676:655.3:628.477.6
Keywords: recycled paper, digital printing,
print quality
Introduction
Paper is the substrate mostly used for the image re- fibers from collected paper [2]. There are two principal
production in digital printing. Hence, the knowledge of types of pulp, depending on the method of the producthe influence of paper on the print quality is necessary to tion: chemical or mechanical. Mechanical pulp is prounderstand and improve the digital printing performance. duced primarily from spruce wood and during the proPrinting companies participate in choosing the paper on duction the fibers are liberated only through mechanical
which something is to be printed. Besides the quality of processing of the wood. In the production of the chemithe paper, environmental consideration is one of the fac- cal pulp, cellulose fibers are extracted by boiling with
tors that influences the choice and therefore they often chemical additives. The chemical pulp consists both of
choose to print on recycled paper.
long-fiber pulp from coniferous trees and of short-fiber
Paper, which is the receiving substrate, is an im- pulp from deciduous trees.
portant component in determining the final print quality.
Recycled paper is a type of paper that completely
Paper consists of randomly distributed fibers – normally or partially consists of recycled fibers. These fibers can
cellulose – joined together in a hydrogen-bonded struc- have very different origins and therefore also very differture as a consequence of the evaporation of water [1]. ent characteristics when it comes to being a component
Various additives can be added, such as adhesive, fillers of the new paper. When producing graphic papers based
and pigments. There are many types of paper. The char- on recycled fibers, the paper mill needs as high quality
acteristics of different papers depend on the raw materi- raw materials as possible. This includes as little ink as
als, the treatment of raw materials, added substances possible to facilitate deinking, or preferably not having
and the final treatment of the paper. The primary mate- deinking at all. Unlike the preparation of the pulp from
rial in the production of paper is pulp which consists of virgin fibers, the fibers obtained from printed recovered
cellulose fibers. The fibers are either fresh fibers from paper must have the ink removed. Large particles of ink
the wood of coniferous and deciduous trees or recycled
that are left in the pulp will result in blemished papers
* Author address: Ivana Jurič, Faculty of Technical Sciences, Department of Graphic Engineering and Design, Trg Dositeja Obradovića 6,
21000 Novi Sad, Serbia
E-mail: rilovska@uns.ac.rs
The manucsript received: April, 1, 2013.
Paper accepted: May, 8, 2013.
26 Advanced technologies
with visible specks of ink. If the ink particles are less than
40 μm in size, the eye cannot resolve them [3]. Recycled
paper also includes a large proportion of the paper from
chemical pulp, which produces the strongest fibers [2].
The concerns with recycled paper are usually about
the fiber qualities. However, the increasing demands
and improvements in technology have been perfecting
the recycled paper quality, as well as driving the cost to
be in the same range compared to the virgin fiber paper
[4]. It is said that recycled paper is more expensive. It is
wrong because recycled paper has aligned with conventional paper prices in recent years due to the increase
in demand, refinement of the papermaking process and
the significant reduction in energy and water necessary
to make recycled paper compared to conventional paper
[5]. The production of the paper from recovered fibers
uses up to 50 % less energy than the production of the
paper from virgin pulp because much of the paper mass
has already been processed. This can also consume up
to 60 % less water [6]. The use of recycled fibers varies
from country to country, and it is dependent on the quantity of pulpwood resources and environmental laws of the
country. In Europe, recycled fibers are generally used
for economic and ecological reasons. In countries like
Japan, Korea, Taiwan and Mexico, the additional reason
to use recycled fibers is the scarcity of native pulpwood
resources [7].
In general, each technique, starting from the conventional to digital ones sets different tasks on the paper
properties in order to satisfy the given principles of the
process [3]. To ensure the best quality and productivity of the digital printing, a number of requirements for
paper properties must be met. While many types and
grades of paper can be run in digital printing systems,
there are a common set of characteristics and the quality criteria that must be built into papers (either recycled
or non-recycled) that are optimized for the performance
in digital printing systems – either monochrome or color.
While some offset sheets may also function, they may
not perform as reliably or produce the same print quality
as papers specifically designed for use in digital printing
systems [8]. For digital printing, the structure and composition together with the electrical and thermal properties of the paper are very important. These paper properties have direct influence on runnability and performance
of digital printing systems. Digital printing is based on a
different image transfer to substrate compared to offset
printing. During the image transfer process, the paper is
subjected to electrostatic charges. If the paper lacks the
proper electrical characteristics, dry ink may not transfer
properly or completely, causing print quality defects or
other failures. Also, the high temperature used for fusing
in most digital printers, combined with the friction of the
paper being moved at high speeds through the system,
can generate static electricity. On the other hand, optical
paper properties have no bearing on runnability and performance, but do have a significant impact on the print
quality. High brightness and whiteness values of papers
2(1) (2013), 26-32
give more contrast, allowing colors to stand out. Low values of brightness and whiteness are easier on the eyes
for periods of extended viewing or reading. Adequate paper brightness enhances the contrast between the paper
and the image, thus improving readability. Opacity is an
important consideration in two-sided printing. Good digital paper must be sufficiently opaque to prevent show
through from the reverse side of a duplexed page, or
from the subsequent pages in a set.
There are several papers investigating the possibility
of using recycled paper in the printing. Grilj et al. [7] compared the electrophotographic print quality on recycled
paper and papers made with virgin fibers in everyday
office use. On the prints, four print attributes were determined: the edge sharpness, print micro-nonuniformity,
color gamut and halftone values. They found that prints
produced on recycled papers and papers made with
virgin fibers have very similar edge sharpness. Prints
produced on 100 % recycled papers achieved slightly
smaller color gamut, but the difference was extremely
small. Malčić et al. [9] examined the influence of natural
and accelerated ageing on optical properties of printed
recycled paper. After ageing, the reflectance of recycled
paper decreases all along the wavelength interval, with
a more significant change in a shorter wavelength range.
The decrease of the reflectance in the blue wavelength
range causes the yellowness color appearance of the
sample, as might be expected. Ageing deteriorates the
optical properties of recycled paper. The study of Wingkono et al. [4] showed a strong correlation between the
paper treatment with ink fixative and the improvement in
the print quality in recycled paper. The surface treatment
improves print quality in recycled paper significantly, especially in areas related to ink fixation, such as optical
density, color richness, and line acuity.
The goal of the present research was to examine
whether the paper made from 100 % waste paper could
replace the paper made with virgin fibers as substrate
in different digital marking engines (technologies) for
monochrome print.
METHODS AND MATERIALS
In this research, we used two different papers. One
standard paper made with virgin fibers (Maestro MONDI) that is most commonly used for daily black and white
digital printing, and one recycled paper that is customized for digital printing (mostly ink jet). Papers had the
same basis weight (90g/m2).
The test image was created with the vector graphic
program Adobe Illustrator CS5 containing different elements used for the print quality control, as shown in
Figure 1. Test image dimensions were 17 x 10 cm. The
elements assessed were lines (1 and 2pt width), different text sizes (6 and 12pt) for the evaluation of the
text readability, patches for the print contrast (lines 0.5
and 1lp/mm) and slanted edge for determination of print
sharpness.
27
Advanced technologies
2(1) (2013), 26-32
region of interest (ROI) was defined as 150 × 300 pixels
and was manually adjusted for each sample in order to
enclose the detected edge more precise.
Figure 2. MTF curve generation: a) ROI, b) ESF function, c)
LSF function, d) SFR/MTF curve
The edge spread function (ESF, which is essentially
the reflectance profile) was obtained from a ROI enclosing the edge. The corresponding line spread function
(LSF) was obtained by taking the first derivative of the
ESF function. The SFR (also called MTF) was obtained
by applying a Fourier transform to the LSF as illustrated in Fig 2d. A characteristic point from MTF curve for
each sample were recorded - the spatial frequency at
response of 50 % (noted as MTF50). It was stated [11]
that the spatial frequencies where MTF was 50 % of its
low frequency value were the best indicators of the image sharpness.
One more print attribute was estimated in the paper
- print contrast. Generally, the print contrast is the difference in reflectance between black and white lines. There
are several methods for obtaining the print contrast. The
most commonly used method is presented in standard
ANSI X3.182. It is called Edge Contrast and it is calculated as follows:
Print Contrast = Rmax - Rmin
[1]
where, Rmax is the average reflectance in the areas between the lines, and Rmin is the average reflectance of
the lines.
Figure 1. Test image
Printing was performed on different digital printing
machines with black ink only. We chose four digital printing machines that are based on different marking engine
(different printing technology):
- Canon IP4800 - ink jet and
- Xerox DocuColor 252 and RICOH MP7500 - electrophotography.
In order to assess the maximum quality one machine
can produce, we chose maximum possible resolutions
for each machine. After printing and drying, the elements
of printed sheets relevant for further analysis were digitalized with Canon CanoScan 5600F scanner. Scanning
resolution was set as 1200 spi and all auto functions were
turned off. This resolution is recommended by standard
ISO 24790 (Information Technology—Office equipment
— Measurement of image quality attributes for hardcopy
output — Monochrome text and graphic images). Substantial image elements were saved as separate tiff files
and the results obtained from the prints were compared
RESULTS AND DISCUSSION
to those acquired from the non-printed (“original”), digital
test form. To calculate the above mentioned parameters,
Line quality
the open source image processing and analysis program
The
results obtained by measuring 1 and 2 pt black
ImageJ [10] and Imatest 3.1 were used.
lines
(horizontal
and vertical) are presented in Tables
The reproduction of the line quality was assessed by
1-4.
The
differences
between the samples printed with
measuring the area and perimeter of 1 and 2 pt thick
the
same
printing
machine
on different paper are very
black lines. In this manner we determined the edge ragsmall
and
insignificant.
gedness for black ink. This phenomenon – also referred
to as wicking – describes the jagged strict edges.
The text quality was determined according to the values Table 1. Area and perimeter of 1pt black line (horizontal)
of the area and perimeter of the positive letter ''T'' (6
and 12pt). The perimeter was calculated by measuring
the outer edge of a letter, while the area was derived
from the corresponding number of pixels representing
the object, i.e., the letter. These parameters are a good
indicator of text readability since significant deviations in
perimeter and area may result in poor readability.
Furthermore, print sharpness was determined. For
*referent values A=5.25mm2 P=30.7mm
the MTF (Modulation Transfer Function) characterization
we used software Imatest 3.1, SFR module. The MTF
curve generating algorithm is presented in Figure 2. The
28 2(1) (2013), 26-32
Advanced technologies
Table 2. Areas and perimeter of 1pt black line (vertical)
Table 3. Area and perimeter of 2pt black line (horizontal)
*referent values A=10.5mm2 P=31.4mm
Table 4. Areas and perimeter of 2pt black line (vertical)
The measured lines were also compared to those
acquired from the non-printed digital test form (Figure
3 and Figure 4). These graphs represent areas and perimeters of 1 and 2 pt black lines printed on different machines. Dashed black lines on each graph represent a
referent value i.e. the value of 1 and 2 pt line area and
perimeter measured on a digital file sent to the printer
(rasterized on 300 dpi).
Figure 3. 1pt black line a) area and b) perimeter (horizontal line)
Figure 4. 2pt black line a) area and b) perimeter (horizontal line)
The lines that are printed with Canon IP4800 ink jet printed vertically on RICOH MP7500 have the minimum
printing machine have the maximum deviation from the deviation. In theory, the samples with a larger perimeter
reference value while the lines that are printed horizon- and a larger area should exhibit poorer edge sharpness
tally with Xerox DocuColor 252 and the lines that are (line quality). Based on this fact we can conclude that
29
2(1) (2013), 26-32
Advanced technologies
the smallest edge sharpness is obtained on the samples printed with Canon IP4800. Lines are very ragged
because of the color spread into the paper. The same
trends were noticed for vertical lines.
was achieved with the Xerox Docu Color 252 printer
and the difference between recycled and non-recycled
paper was minimum. The smallest print sharpness was
obtained for the sample printed on recycled paper with
Canon IP4800 ink jet printer (3.33 cy/mm). The values
Text readability
are presented in two units: cy/mm (cycles per millimeter)
Text readability was evaluated on the basis of the and LW/PH (line widths per picture height). According to
area and perimeter of the letter ''T'' (6 and 12pt). Ac- the second unit, the print sharpness can be defined for
cording to the scanned word ''Text'' (6pt font size) pre- the exact picture height that will be printed [11].
sented in Figure 5 it can be concluded that the poorest We also assessed the print sharpness for a horizontal
text readability is achieved on the samples printed with slanted edge. The results are presented in Table 8. BasiCanon. The text printed with RICOH and Xerox is crisp cally, MTF50 values are larger than those for the vertical
and has smooth edges. The edges of the letters are very line that indicates larger print sharpness. This is probacoarse and ragged. This was also obtained by objective bly due to the influence of direction of paper fibers which
measurements of the area and perimeter of the letter ''T'' are parallel with the lines.
which was compared with the referent value. The results
are summarized in Tables 5-6. Based on these results, Table 7. Print sharpness for a vertical slanted edge
no significant differences were found between the prints
on the papers made with virgin and recycled fibers.
Figure 5. Word “Text” printed with black ink by: Canon on a)
recycled paper – lenza, b) non-recycled paper – mondi; RICOH
c) lenza, d) mondi and Xerox e) lenza, f) mondi
Table 8. Print sharpness for a horizontal slanted edge
Table 5. Area and perimeter of 6pt text letter ‘’T’’
*referent values A=0.38mm2 P=4.49mm
Table 6. Area and perimeter of 12pt text letter ‘’T’’
*referent values A=1.39mm2 P=9.38
Print Sharpness
In Table 7, MTF values for all printed samples are
summarized. MTF values were calculated according to
ROI areas presented in Figure 6. As it could be expected,
compared to previous results the largest print sharpness
30 Print Contrast
The results obtained by measuring the print contrast
for 0.5 and 1 lp/mm frequencies are shown in Table 9.
At lower frequencies, the contrast between the paper
brightness and ink reflectance was larger. Clearly, as the
frequency increased, the print contrast decreased. The
largest print contrast was achieved when the printing
was performed with printing machines based on electrophotographic printing process (RICOH MP7500 and
Xerox DocuColor252). Generally, a larger print contrast
was achieved on the paper made with virgin fibers. This
result could be explained by this paper being whiter
(WCIE=114.881) than the paper made from 100 % waste
paper (WCIE=104.97). When the paper is whiter, the average reflectance in the areas between the lines (Rmax) is
larger. This results in a higher print contrast.
1
Whiteness was measured with spectro densitometer SpectroDens
using CIE Whiteness formula.
2(1) (2013), 26-32
Advanced technologies
Table 9. Print contrast for 0.5lp/mm and 1lp/mm
Abbreviations and symbols
MTF - Modulation Transfer Function
ROI - Region of interest
SFR - Spatial Frequency Response
ESF - Edge spread function
LSF - Line spread function
CIE - Commission Internationale de l'Eclairage
CONCLUSIONS
The perception of the print quality is based on a number of print attributes. The attributes such as the line
reproduction, text quality (readability), print sharpness
and print contrast can be good indicators of the maximum possibility of the printing device (print quality). The
main goal of this research was to investigate the possibility of using recycled instead of non-recycled paper in
digital printing. It was also examined how these papers
behaved on different digital marking engines (technologies). On the prints, four different print attributes were
determined by using the image analysis method. According to the results obtained in this paper, the differences
between 100 % recycled paper and the paper made with
virgin fibers were extremely small. The only difference
was observed when the prints were printed with different
printing machines, as expected. The largest deviations
from referent values were noticed for the prints printed
with ink jet printing machines (Canon IP4800). It was
evident that as deviations were larger, the readability of
the text was lower and the edge raggedness was larger
and vice versa. The difference was also observed when
the attributes were obtained according to the horizontal
and vertical elements. This was probably due to the influence of the direction of paper fibers and the direction of
printing. The print contrast results indicate that the optical paper property, such as whiteness, had impact on the
print quality. Slightly better quality, in terms of the print
contrast was achieved on the paper made with virgin fibers which is whiter than recycled paper.
Generally, based on the print quality results obtained
in this research, 100 % recycled paper achieved a high
print quality. Hence, for monochrome digital printing, the
papers made with virgin fibers could be entirely replaced
with the 100 % recycled papers. The results of this study
will encourage the use of recycled papers for digital
printing, knowing how much it will contribute to preserving the environment.
REFERENCES
[1] M. A. Hubbe, J. J. Pawlak, and A. A. Koukoulas (2008).
Paper's appearance: A review, BioResources 3 (2), pp627-665
[2] M. Silfverstolpe (2008) Recycling of printed products, The
environmental council of the Swedish printing industries,
Belgium
[3] B. Thompson (2004): Printing materials: Science and
technology: A Pira International printing guide, Pira
International, Leatherhead
[4] G. Wingkono, T. R. Oswald and J. Stoffel (2011) Surface
Treatment to Improve Print Quality on Recycled Paper,
NIP 27 and Digital Fabrication 2011, Technical Program
and Proceedings
[5] A local printer (2013): Recycled Printing and Paper - The
Facts [Online] Avaiable at: http://www.alocalprinter.com/
uk/recycled-paper/ (Accessed: 17.1.2013)
[6] Know your printing paper, A guide to purchasing recycled
content printing paper for corporate stationery and
promotional materials, The Department of Environment
and Climate Change (NSW), ISBN 978 1 74232 095 3
[7] S. Grilj, T. Muck, A. Hladnik, and D. Gregor-Svetec (2012)
Recycled papers in everyday office use, Nordic Pulp and
Paper, Research Journal, Volume 27, 2012, Issue No. 4,
pp. 739-749
[8] Xerox Corporation (2004): Helpful facts about the paper
[Online] Available at: http://www.xerox.com/downloads/
usa/en/s/supp_lib_Helpful_Facts_About_Paper.pdf (last
visited: 16.12.2012.)
[9] V. Džimbeg-Malčić, M. Dadić and Z. Bolanča (2003)
Optical Properties of printed recycled paper exposed
to ageing, 11th Color Imaging Conference, IS&T/SID
Eleventh Color Imaging Conference, pp. 255-260
[10]W. S. Rasband (2011): ImageJ, U. S. National Institutes of
Health, Bethesda, Maryland, USA, [Online] Available at:
http://rsbweb.nih.gov/ij/ (last visited: 16.1.2013.)
[11] N. Koren (2009) Imatest Documentation, Technical
documentation for Imatest 3.1 Master software
ACKNOWLEDGEMENTS
This work was supported by the Serbian Ministry of Education, Science and Technological Development, Grant
No.: 35027 "The development of software model for the
improvement of knowledge and production in graphic arts
industry".
31
2(1) (2013), 26-32
Advanced technologies
Izvod
MOGUĆNOST UPOTREBE RECIKLIRANOG PAPIRA U DIGITALNOJ ŠTAMPI
Ivana Jurič, Dragoljub Novaković, Igor Karlović, Ivana Tomić
Fakultet tehničkih nauka, Departman za grafičko inženjerstvo i dizajn, Univerzitet u Novom Sadu,
Novi Sad, Srbija
Potreba za recikliranim papirima se povećala tokom poslednjih godina. Osnovni motiv upotrebe recikliranog papira je smanjenje troškova. Cilj korišćenja
recikliranog papira je prikupljanje već upotrebljenog papira. Ovo je prvobitno
bilo primenjeno u zemljama koje imaju jako malo šuma. Danas su glavni motiv ekološki problemi. Cilj ovog rada je ispitivanje mogućnosti upotrebe 100%
recikliranog papira umesto papira napravljenih od celuloznih vlakana u digitalnoj štampi za monohromatske otiske. Papiri su štampani na tri različite digitalne mašine. Xerox DocuColour 252 i RICOH MP7500 su bazirani na principu
elektrofotografije, a Canon IP4800 je baziran na ink džet principu štampanja.
Korišćenjem metode analize slike kontrolisani su kvalitet reprodukovane linije,
čitljivost teksta, oštrina štampe i kontrast. Rezultati dobijeni kontrolom kvaliteta
štampe na recikliranom papiru su bili obećavajući. Otisci štampani na recikliranom papiru su postigli sličan, u nekim slučajevima potpuno isiti kvalitet kao
i otisci štampani na papiru od celuloznih vlakana.
32 (ORIGINAL NAUČNI RAD)
UDK 676:655.3:628.477.6
Ključne reči: recikliran papir, digitalna štampa,
kvalitet štampe