1. International Paper - Papermaking
Process Solutions
Brightness (3 Types) &
Whiteness (2 Types):
Full Disclosure
CRABLE ENGINEERING LLC
2. Informing our Customers:
CRABLE ENGINEERING LLC
“Marketing psychologists state that a
lasting impression is made within ninety
seconds and that color accounts for 60%
of the acceptance or rejection of an object,
person, place, or circumstance. Because
color impressions are both quick and long
lasting, decisions about color are critical
factors in the success of any visual
experience.” - About Color
The fields of shade (or color) and appearance are
critical to the acceptance of paper and board products,
yet these product attributes are often overlooked.
Or, systems to support them are often an afterthought
in the design of papermachine processes.
3. Definition & Origin of Brightness
It is the measure of light reflected from a
sample at 457 nanometers +/- 44 nm.
Brightness represents the diffuse blue
reflectance of a sample, and the
wavelengths indicated above were chosen
on a somewhat arbitrary basis.
It was introduced as a visual aid for
assessing and controlling the degree of
pulp bleaching.
Informing our Customers:
CRABLE ENGINEERING LLC
4. Origin & Evolution of Brightness
Originally, brightness was assessed by
observing a pulp sample through a blue-
stained glass.
The more the pulp is bleached, the more
lignin is removed, and the higher the “blue
reflectance” becomes.
The reason for focusing on the blue-yellow
axis is that the pulp starts out dark brown,
changes to light brown, then to tan, and to
diluted yellow as bleaching progresses.
Informing our Customers:
CRABLE ENGINEERING LLC
6. Origin & Evolution of Brightness
The need to simplify and standardize
bleaching assessment of pulp led to the first
instruments such as the GE-Photovolt.
General Electric has long since sold this
instrument business, but the term GE
brightness remains. (Technidyne currently
produces the instruments to measure it.)
In this instrument, samples are illuminated
with an incandescent lamp at a 45o angle
and reflectance is measured perpendicularly
or at a 0o angle of observation.
Informing our Customers:
CRABLE ENGINEERING LLC
7. Evolution and Use of Brightness
As there was no comparable instrument
available for the papermaking process, the
GE brightness meter (now referred to as
Directional or TAPPI T452 Brightness)
moved to the paper mill.
Prior to the introduction of fluorescent
whitening agents, and as a consequence of
its purpose in describing the degree of
bleaching, brightness over time became
synonymous with how white the paper
appeared (or simply whiteness).
Informing our Customers:
CRABLE ENGINEERING LLC
8. Types of Brightness
There are two basic types of brightness
measurement: Directional and Diffuse.
Directional brightness (TAPPI brightness –
TAPPI 452) employs the 450/00 geometry of
the original GE-Phovolt instrument. It has
been the standard in the U.S. and Japan.
Diffuse brightness employs a D/00 geometry
where D indicates diffuse illumination from
a sphere, making it insensitive to sample
orientation. Diffuse brightness is the
standard in much of the rest of the world.
Informing our Customers:
CRABLE ENGINEERING LLC
10. Types of Brightness
Two types of Diffuse brightness are commonly
discussed, and a standard exists for both of them.
ISO C Brightness (ISO 2470-1, TAPPI 525) uses
Illuminant C level of UV energy. It was selected as
the best approximation of normal office lighting
conditions.
ISO D65 Brightness uses Illuminant D65
(daylight). Control of D65 level of UV energy is
not good from instrument to instrument, but still
there is now a standard for D65 Brightness (ISO
2470-2).
Informing our Customers:
CRABLE ENGINEERING LLC
12. Comparison of Brightness Types
TAPPI (450/00) , or Directional and Diffuse
(D/00) Brightness (C or D65) cannot be
correlated. This is due to the fact that
multiple reflections which occur between
the sphere and sample make unpredictable
changes in Diffuse Brightness as compared
to Directional (TAPPI) Brightness.
The following two slides show brightness
comparisons on a number of white papers.
Informing our Customers:
CRABLE ENGINEERING LLC
13. Brightness Comparisons
Technidyne Technidyne
Sample D65 Brightness ISO Brightness TAPPI R457 C S-4M
A 98.92 91.78 89.9 6.93 5.2
B 95.34 88.99 87.3 6.14 4.7
C 105.58 95.08 91.8 10.58 7.9
D 111.20 99.83 96.5 11.48 8.5
E 110.61 98.94 95.5 11.90 9.2
F 112.25 100.43 96.0 12.58 9.5
G 113.46 100.89 96.4 13.45 10.3
H 110.11 98.68 94.7 11.73 8.8
I 112.28 100.15 95.9 12.97 9.8
J 93.00 88.64 90.0 5.44 4.3
K 102.01 92.52 90.6 9.56 8.0
L 110.12 99.05 95.0 12.08 9.1
M 110.14 99.48 96.1 10.97 8.4
N 107.24 96.68 94.1 10.66 8.1
O 106.90 96.28 93.0 10.61 7.9
P 110.31 99.21 96.1 11.51 8.9
Q 109.57 99.03 96.1 10.90 8.2
R 113.86 101.50 97.4 13.25 10.3
S 111.55 99.29 95.0 12.80 9.6
T 85.48 85.43 87.6 0.02 0.0
Elrepho
Brightness
Elrepho
Fluorescence
Informing our Customers:
CRABLE ENGINEERING LLC
15. The Scattering Properties of
Glossy and Matt Samples
GLOSSY SURFACE MATT SURFACE
The surface properties of a sample influence the
quality and quantity of light that reaches our eye;
influencing the way an object appears.
In fact, we sometimes calender samples to get “the
right look.”
Specular Reflection
Diffuse Reflection
Informing our Customers:
CRABLE ENGINEERING LLC
16. Problems and Limitations of Use
Directional (TAPPI) brightness, first, has an issue in
that it is highly sensitive to fiber angle. Indeed, one
can impact directional brightness with changes in
Rush/Drag ratio.
Per TAPPI method T 452, section 1.2: “This
procedure is applicable to all naturally-colored
pulps, and papers and board made therefrom. The
measurement is not suitable for paper or paperboard
containing coloring matter (such as yellow or green
dyestuff) which appreciably absorbs light in that part
of the spectrum extending from 400 to 500 nm.
Colored papers must be measured
spectrophotometrically or colorimetrically in order
to obtain meaningful results.”
Informing our Customers:
CRABLE ENGINEERING LLC
17. Problems and Limitations of Use
The biggest issue with use of brightness as a paper
metric, though, is that it measures reflectance in a
VERY narrow (blue) band of the reflectance
spectrum. This does not correlate well with the
perception of whiteness or visual appeal.
Also, brightness is not a linear function. A change
from 84 to 90 brightness has much more visual
impact than a change from 90 to 96 brightness.
The higher the brightness of the paper (brought
about through the use of FWA), the quicker the
paper will fade.
Informing our Customers:
CRABLE ENGINEERING LLC
18. Ways to Increase Brightness
Start with brighter pulp. This could involve
additional bleaching or washing of the pulp or even
purchase of High Brightness pulp.
Cover the fiber with fillers of higher brightness.
E.g. use very bright clay, PCC, TiO2, or ATH to
hide the yellower fiber.
Use Fluorescent Whitening Agents (FWA) to
“boost” the blue reflectance measured as
brightness.
Keep the FWA on the surface of the sheet using
good film formers such as PVOH or PEG.
Use the cleanest, brightest coatings (starch or
PVOH in uncoated paper) possible.
Informing our Customers:
CRABLE ENGINEERING LLC
19. Ways to Avoid Lower Brightness
Use no post-consumer fiber (contains more
fines and contaminants) which dull the paper.
Avoid heavy metal ions (such as copper,
manganese, and iron) in the process. Use a
chelant to control them if necessary.
Treat very hard water to prevent precipitation
of the FWA.
Do not overuse FWA or “green-over” may
occur.
Use minimum amounts of dye for shade
control. Informing our Customers:
CRABLE ENGINEERING LLC
20. CIE Whiteness
Whiteness is a visual perception that
involves the entire visible spectrum from
400 nm to 700 nm.
It was developed, specifically, as a single
metric to describe the appearance and appeal
of white papers.
Values of Whiteness increase as the paper
becomes bluer and slightly redder.
Whiteness can be increased both through use
of FWA and tinting dyes.
Informing our Customers:
CRABLE ENGINEERING LLC
21. CIE Whiteness
Most import papers are shade formulated to
take advantage of the increase in Whiteness
with blue and red (or violet) tinting of the
paper.
Whiteness can be less expensive to achieve
than Brightness: a small addition of tinting
dye (low cost) can significantly improve
Whiteness. [Tinting dye use can generally
only lower Brightness.]
Change in the shade of paper with light
exposure is generally less severe than loss of
Brightness with FWA fade.
Informing our Customers:
GREENVILLE COLORANTS LLC
22. CIE Whiteness
There are two types of CIE Whiteness.
First is outdoor CIE Whiteness (per ISO 11475).
It yields the higher value due to the higher UV
energy level of Illuminant D65. It came first and
is the only one commonly used.
Second is indoor CIE Whiteness (per ISO 11476).
It yields lower values but is more representative of
office lighting conditions, using the UV energy
level of Illuminant C.
CIE Whiteness should ONLY be used for ‘near-
white’ papers. (And this is becoming an issue.)
Informing our Customers:
CRABLE ENGINEERING LLC
24. Brightness Conclusions
Either brightness or whiteness can be more
expensive to achieve depending upon the
shade of the paper and its ‘brilliance’.
As one goes to very high brightness levels,
production costs rise ever more quickly, and
the visual impact becomes smaller.
ISO Brightness values are generally higher
(as much as 1.5 to 4.5 points) and less
variable than TAPPI Brightness values.
Whiteness often correlates better with visual
appeal than does Brightness.
Informing our Customers:
CRABLE ENGINEERING LLC
25. Whiteness Conclusions
The uppermost Whiteness values have now been
pushed beyond their practical limits for true white
papers.
As one goes to very high whiteness levels, the
positive impacts of FWA on the paper have been
exhausted.
The only way to continue to increase CIE
Whiteness, then, is to make the paper bluer.
Often, however, the product begins to look dull
and grayish at the highest CIE Whiteness levels.
We need to refine the CIE Whiteness equations to
prevent overuse of tinting dyestuff to artificially
inflate the numerical value while actually making
the paper look duller.
Informing our Customers:
CRABLE ENGINEERING LLC
26. Whiteness Conclusions
Although much of the rest of the world makes
and sells paper according to CIE Whiteness
level (which is not printed on packaging) the
attempt to introduce whiteness into the U.S.
market was not well received.
Much of the reason for this is that major U.S.
customers are familiar with brightness (mostly
TAPPI T452 brightness) and are unwilling to
give up this metric.
Brightness is still printed on the ream wrap
and, oddly, is used to distinguish between
quality levels. Informing our Customers:
CRABLE ENGINEERING LLC
