Textile Coloration Theory

1. TEXTILE COLORATION THEORY
PREPARED
BY
SHAHARIA
AHMED

2. Color is an aspect of visual
perception dependent on the
spectral composition of observed
radiant energy.
Color is physical impression of
human mind. It is impossible to
measure.

3. BASIC NORMS OF COLOR SCIENCE
Color: The visual effect that is caused by the spectral composition of
the light emitted, transmitted, or reflected by objects.
Color Temperature
A color temperature meter measures the color temperature of an incident
illuminant.The temperature, in Kelvin, of a Planckian black body
radiator whose radiation has the same chromaticity
coordinates as that of a given stimulus.
Fluorescence
The process whereby colors absorb radiant power at one wavelength
and immediately re-emit it at another (usually longer) wavelength,
as in "day-glo" or black-light paints.
Hue
The attribute of a visual sensation according to which an area appears to
be similar to one, or to proportion of two, of the unique hues: red,
yellow, green and blue.

4. Light
A universal and essential attribute of all perceptions
and sensations that are peculiar to the visual
system. In other words, an optical radiation capable
of directly causing a visual sensation.
Luminescence
Luminescence may occur either during or after the
absorption of light energy at another wavelength.
Emission which occurs only as long as the exciting
input is being received is specified by the term
fluorescence; emission which continues for some
time after the energy input has ceased (as on the
dial of an alarm clock) is said to exhibit 'afterglow'
or the attribute of so-called phosphorescence.

5. The wavelengths of the complete visible
spectrum, between infrared and ultraviolet,
range from approximately 390 to 750 nm
(nanometers, billionths of a meter). Spectral
wavelengths are also frequently given in Å
(angstroms, 10 nm) or °K (degrees Kelvin).
While active upon the human body, ultraviolet
and infrared are invisible to the human eye.
These are the wavelengths for the traditional
visible "seven colors of the rainbow", VIBGYOR:
430-390
Violet
450-440
Indigo
480-460
Blue
530-490
Green
580-550
Yellow
640-590
Orange
750-650
Red

6. Color, wavelength, frequency and energy of light
Color
(nm) (THz) (μm−1) (eV) (kJ mol−1)
Infrared >1000 <300 <1.00 <1.24 <120
Red 700 428 1.43 1.77 171
Orange 620 484 1.61 2.00 193
Yellow 580 517 1.72 2.14 206
Green 530 566 1.89 2.34 226
Blue 470 638 2.13 2.64 254
Violet 420 714 2.38 2.95 285
Near ultraviolet 300 1000 3.33 4.15 400
Far ultraviolet <200 >1500 >5.00 >6.20 >598

8. Spectrophotometer:
The spectrophotometer is a physical tool which is eminently suited to measure
the most important variable of all, the shade and strength of the dyestuffs
themselves, whether they be in solution or on the fiber. Spectrophotometer
used by dyeing factory and colorant manufacturers all over the world.
Normally Color lab manager analysis the color of swatch with the help of
spectrophotometer.

9. TYPES OF SPECTROPHOTOMETER
Spectrophotometers measure reflected or transmitted light across a light spectrum. The
resulting data creates a visual curve. Spectral data is invaluable to anyone in the printing
trades. Spectral measurements ensure that color is consistent across varying substrates and
production processes. A densitometer checks density but does not see color, and this can often
result in color variations that might not meet customer expectations.
Spherical Spectrophotometers

10. 0º/45º (OR 45º/0º) SPECTROPHOTOMETERS
This is simply because a human viewer does everything in his or her power to
exclude the “specular component” (gloss) when judging color. When we look at
pictures in a glossy magazine, we arrange position so that the gloss does not reflect
back to the eye. A 0º/45ºinstrument, more effectively than any other, will remove
gloss from the measurement dynamics and measure the appearance of the sample
exactly as the human eye would see it. Because 45° instruments perceive color in
the same way as the human eye, they are generally preferred for applications such
as measuring color on smooth or matte surfaces. They are not necessarily the best
choice for measuring color on glossy and reflective surfaces.

11. MULTI-ANGLE SPECTROPHOTOMETERS
Automotive manufacturers have created and refined automotive coatings to
present a unique experience when viewing a vehicle. They have
experimented with special effect colors using special additives such as
mica, pearlescent materials, ground-up seashells, specially coated pigments
in order to produce a surface that shifts in color when viewed from different
angles. Large and expensive goniometers were traditionally used to
measure these colors until X- Rite introduced a battery-powered, hand-held,
multi-angle instrument.

12. Color measurement procedure consists of 5 steps:
1.Prepare samples to make colored compound
2.Make series of standard solutions of known concentrations
and treat them in the same manner as the sample for making
colored compounds
3.Set spectrophotometer to l of maximum light absorption
4.Measure light absorbance of standards
5.Plot standard curve: Absorbance vs. Concentration,
Spectrophotometers measure reflected or transmitted light
across a light spectrum. The resulting data creates a visual curve.
Spectral measurements ensure that color is consistent across
varying substrates and production processes. A densitometer
checks density but does not see color, and this can often result in
color variations that might not meet customer expectations.

13. Instruments for Measuring Transmittance
The measurement of dyes in solution to verify the color quality and strength is themost
common application, although the measurement of transparent films is also used. Most
spectrophotometers for measuring liquids are designed such that a transmission cell or
cuvet is inserted between the detector

14. DUAL- BEAM SPECTROPHOTOMETER

15. Functions of spectrophotometer:
1.Color difference
2.Metamerism
3.Pass/fail operation
4.Fastness rating
5.Shade library
6.Cost comparison
7.Color match production
8.Reflectance curve.

16. Flow Chart of Color Matching Process with Spectrophotometer:

17. COLOR MEASUREMENTS
The human eye has a spectral sensitivity that peaks at around 555 nm,
which means that the color green gives an impression of higher
brightness than other colors. At 490 nm the sensitivity is only 20%
compared to the sensitivity at 555 nm. Furthermore, the human eye can
only distinguish about 10 million different colors which is actually quite
limited relative to the needs of color measurement applications.
Spectrometers are designed to measure exact wavelengths, and are
therefore ideal for color measurements.
Color measurements may be applied to a variety of industrial
applications such as color of textile, paper, fruit, wine, and bird
feathers. Avantes has developed a variety of custom probes to meet the
specific demands of the color measurement application. Color
measurements are manifested in the L*a*b* color model which includes
parameters for brightness and hue.

18. FIGURE : 1931 X,Y CHROMATICITY DIAGRAM
Hue is the term used for general classification of color—the region of the
visible spectrum (380 to 700 nm)—in which the greatest reflectance of
light occurs. Hues perceived as blue tend to reflect light at the lower end
of the spectrum, greens in the middle region, and reds toward the higher
end. Above slide shows spectral sensitivity corresponding to that of the
human eye.

19. X-Y-Z VALUES AND YXY COLOR SPACE
One of the earlier color space representations is the CIE 1931X,Y
chromaticity diagram, as shown in figure 2. The diagram is used
for 2-D graphing of color, independent of lightness. X and Y are
the chromaticity coordinates calculated from the tristimulus
values X-Y-Z. In this diagram, achromatic colors are toward the
center, and chromaticity increases toward the edges. A
colorimetrically measured red apple whose chromaticity
coordinates are X = 0.4832and Y = 0.3045can be located in this
color space at position A (the blue circle).
Also referred to as CIELAB, L*a*b* color space was promulgated in 1976 to adjust
for one of the problems of the original Yxy color space. Equal distances on the X,Y
chromaticity diagram did not correspond to equally perceived color differences. In
the L*a*b* diagram, a spherical color solid, L* indicates lightness, and a* and b*
are the chromaticity coordinates. Here the a* and b* indicate color directions (+a*
is the red direction, -a* is the green direction).

20. L*C*h color space uses the same diagram as L*a*b* color space, but
employs cylindrical rather than rectangular coordinates. L* is the
same as the L* of the L*a*b* diagram. C* is chroma, and h is the hue
angle. The value of C* is zero at the center for an achromatic color,
and increases according to the distance from the center. Hue angle
(h) is defined as starting at the +a* axis and is expressed in degrees as
the chroma axis rotates counterclockwise.
Measurement output from a colorimeter is expressed in terms of X-Y-
Z values for the measured sample, as well as in units of other
accepted uniform color spaces. By comparing measurements of target
colors with sample specimens, the user obtains not only a numerical
description of a color, but can also express the nature of a color
difference between two measured specimens. The colorimeter
pinpoints the difference in lightness, chromaticity, and hue between
the target and the sample.

21. FIGURE 3: A*, B* CHROMATICITY DIAGRAM

22. Color measurements taken in one location and expressed in
units of a given color space then can be compared with
measurements taken in another location or at another time
and communicated in an internationally accepted language. In
this manner, colorimetric measurement eliminates subjectivity
in color perceptions and color difference judgments.
Color space A system for ordering colors that respects the
relationships of similarity among them. There are variety of
different color spaces, but they are all three dimensional.
The two most widely known's of these methods are the Yxy color
space, devised in 1931based on the tristimulus values XYZ defined
by CIE, and the L*a*b* color space, devised in 1976to provide more
uniform color differences in relation to visual differences. Color
spaces such as these are now used throughout the world for color
communication.

24. THE MUNSELL SCALE
In 1905, artist Albert H. Munsell originated a color ordering system —or
color scale — which is still used today. The Munsell System of Color
Notation is significant from a historical perspective because it’s based on
human perception. Moreover, it was devised before instrumentation was
available for measuring and specifying color. The Munsell System assigns
numerical values to the three properties of color: hue, value and chroma.
Adjacent color samples represent equal intervals of visual perception. The
model in Figure 4 depicts the Munsell Color Tree, which provides physical
samples for judging visual color. Today’s color systems rely on instruments
that utilize mathematics to help us judge color.
Three things are necessary to see color:
• A light source (illuminant)
• An object (sample)
• An observer/processor

25. THEORY OF COLOR MIXING

26. ADDITIVE O R LIGHT T H E O RY

27. SUBTRACTIVE O R PIGMENT T H E O RY

28. THREE DIMENSIONAL C O L O R SYSTEM

29. The most Popular Norm lights
LightSource Specification ColorTemperature
Day light D65 International standardArtificial daylight-
400-700nm
6500K
Incandescent LightA CoolWhite Fluorescent.USA shoplight
source-405,436,546 and 578nm
4200K
Department store light-CWF /F2 Fluorescent Lamp 4230K
Department store light-TL84/F11 Fluorescent Lamp 4o00K
Ultraviolet Light-UV Ultraviolet lamp;365nm -
Light source F Sun setting light .Yellow lightSource 2700K

31. PASS

32. WHEN CMC VALUEWARN

33. WHEN CMC VALUE ISFAIL

34. Metamerism Index

35. THANK YOU