1) The document discusses measured reflectance (Rλ) values, which represent the fraction of light reflected by a sample at each wavelength, and how these values are independent of the light source used to measure them.
2) It explains that to calculate the actual amount of light reflected at each wavelength, the measured Rλ values need to be multiplied by the energy (Eλ) of the light source at that wavelength.
3) The total amount of light reflected across the visible spectrum is calculated by summing the amounts reflected (Eλ x Rλ) at each wavelength between 380-760nm.
Mordanting
Mordants are used to improve the bond between the dye and the fabric, as well as extending the range of hues that can be obtained from the dyestuff. To make the mordant take better, an ‘assistant’ can be added, which may mean less mordant is needed. The main problem is that typical mordants are based on heavy metals which are extremely toxic, causing environmental problems and presenting health threats to workers if not properly trained.
Dyes: Definition – Requirements of a dye - Theories of colour and chemical constitution - Structure and
applications of Martius yellow, indigo and alizarin.
Natural dyes are dyes or colorants derived from plants, invertebrates, or minerals. The majority of natural dyes are vegetable dyes from plant sources roots, berries, bark, leaves, and wood and other biological sources such as fungi and lichens.Archaeologists have found evidence of textile dyeing dating back to the Neolithic period. In China, dyeing with plants, barks and insects has been traced back more than 5,000 years. The essential process of dyeing changed little over time. Typically, the dye material is put in a pot of water and then the textiles to be dyed are added to the pot, which is heated and stirred until the color is transferred. Textile fibre may be dyed before spinning (dyed in the wool), but most textiles are yarn-dyed or piece dyed after weaving. Many natural dyes require the use of chemicals called mordants to bind the dye to the textile fibres; tannin from oak galls, salt, natural alum, vinegar, and ammonia from stale urine were used by early dyers. Many mordants, and some dyes themselves, produce strong odors, and large-scale dyeworks were often isolated in their own districts. Natural dyes are dyes or colorants derived from plants, invertebrates, or minerals.
MARKET OUTLOOK
The market outlook and growth prospects of the global dyes and pigments market for 2016-2020. The market is further categorized into three product segments, which include dyes, organic pigments and inorganic pigments. The report also segments the market on the basis of type, end-users and geography.
While the global dyes market will grow at a cagr of 3.9% between 2015 and 2020, the global pigments market will register a cagr of 4.05%. Dyes and pigments are used in various end-use applications like dye colorants for textiles, pigmented inks for printing inks, tinting and shading resins of plastics, and as colorants for paints and coatings, and the considerable growth potential of these industries bodes well for the global dyes and pigments market.
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Architectural Paint and Colour Consultant Patrick Baty
The consultancy services offered by Patrick Baty. Advice on the selection of paint colours in buildings historic or otherwise. Paint analysis; colour measurement and matching; colour surveys and technical advice. He has written and lectured widely on the use of paint and colour in historic buildings.
Mordanting
Mordants are used to improve the bond between the dye and the fabric, as well as extending the range of hues that can be obtained from the dyestuff. To make the mordant take better, an ‘assistant’ can be added, which may mean less mordant is needed. The main problem is that typical mordants are based on heavy metals which are extremely toxic, causing environmental problems and presenting health threats to workers if not properly trained.
Dyes: Definition – Requirements of a dye - Theories of colour and chemical constitution - Structure and
applications of Martius yellow, indigo and alizarin.
Natural dyes are dyes or colorants derived from plants, invertebrates, or minerals. The majority of natural dyes are vegetable dyes from plant sources roots, berries, bark, leaves, and wood and other biological sources such as fungi and lichens.Archaeologists have found evidence of textile dyeing dating back to the Neolithic period. In China, dyeing with plants, barks and insects has been traced back more than 5,000 years. The essential process of dyeing changed little over time. Typically, the dye material is put in a pot of water and then the textiles to be dyed are added to the pot, which is heated and stirred until the color is transferred. Textile fibre may be dyed before spinning (dyed in the wool), but most textiles are yarn-dyed or piece dyed after weaving. Many natural dyes require the use of chemicals called mordants to bind the dye to the textile fibres; tannin from oak galls, salt, natural alum, vinegar, and ammonia from stale urine were used by early dyers. Many mordants, and some dyes themselves, produce strong odors, and large-scale dyeworks were often isolated in their own districts. Natural dyes are dyes or colorants derived from plants, invertebrates, or minerals.
MARKET OUTLOOK
The market outlook and growth prospects of the global dyes and pigments market for 2016-2020. The market is further categorized into three product segments, which include dyes, organic pigments and inorganic pigments. The report also segments the market on the basis of type, end-users and geography.
While the global dyes market will grow at a cagr of 3.9% between 2015 and 2020, the global pigments market will register a cagr of 4.05%. Dyes and pigments are used in various end-use applications like dye colorants for textiles, pigmented inks for printing inks, tinting and shading resins of plastics, and as colorants for paints and coatings, and the considerable growth potential of these industries bodes well for the global dyes and pigments market.
See more
https://goo.gl/gGrVe6
https://goo.gl/JQm2aX
Contact us:
Niir Project Consultancy Services
106-E, Kamla Nagar, Opp. Spark Mall,
New Delhi-110007, India.
Email: npcs.ei@gmail.com , info@entrepreneurindia.co
Tel: +91-11-23843955, 23845654, 23845886, 8800733955
Mobile: +91-9811043595
Fax: +91-11-23845886
Website: www.entrepreneurindia.co , www.niir.org
Architectural Paint and Colour Consultant Patrick Baty
The consultancy services offered by Patrick Baty. Advice on the selection of paint colours in buildings historic or otherwise. Paint analysis; colour measurement and matching; colour surveys and technical advice. He has written and lectured widely on the use of paint and colour in historic buildings.
How To Determine The Colour Of Transition Metal ComplexesDenison Dwarkah
Many times students ask the question as to how do we figure out what colour a complex will be. This is a basic starting point and applies to the CAPE Chemistry Syllabus, Module 3 Section 5.
This paper shows my findings for determining the grating constant of a diffraction grating, the wavelengths of each line of the spectrum of hydrogen, and experimentally calculating the Rydberg constant.
UV-visible spectroscopy is a fast analytical technique that measures the absorbance or transmittance of light. Although the UV wavelength ranges from 100–380 nm and the visible component goes up to 800 nm, most of the spectrophotometers have a working wavelength range between 200–1100 nm.
The practical range for UV-vis spectroscopy varies from 200–800 nm; above 800 nm is infrared, while below 200 nm is known as vacuum UV. The ability of matter to absorb and to emit light is what defines its color and the human eye is capable of differentiating up to 10 million unique colors. Light passes through media (transmission), reflects off both opaque and transparent surfaces, and is refracted by crystals. Covalently unsaturated compounds with electronic transition energy differences equivalent to the energy of the UV-visible light absorb at specific wavelengths. These compounds are known as chromophores and are responsible for their color. Covalently saturated groups that do not absorb UV-visible electromagnetic radiation but affect the absorption of chromophore groups are called auxochromes. When UV-vis radiation hits chromophores, electrons in the ground state jump to an excited state, which we refer to as electron-excitation, while auxochromes are electron-donating and have the capacity to affect the color of choromophores while they do not change color themselves. Water and alcohols are mostly transparent and do not absorb in the UV-vis range and so are excellent mediums for UV-visible spectroscopy. Acetone and dimethylformamide (DMF) are good solvents for compounds insoluble in water and alcohol, but they absorb light below 320 and 275 nm, respectively, so are appropriate only above these cut-off wavelengths.
2. Measured Reflectance Rλ
Suppose that we have a sample, such as a painted surface,
and that we have measured
the fraction of light reflected
at each wavelength, Rλ.
Provided that the sample is not fluorescent, the Rλ values will
be completely independent of the light shone on the sample.
(Many instruments give readings in terms of the percentage of
light reflected, i.e. Rλ ´ 100, but fractions are easier to use
in the present discussion.)
.
2
3. Measured Reflectance Rλ
For example, a white paint will reflect
about 90% of the incident light
(i.e. Rλ= 0.9) at, say, 500 nm
Whether illuminated with strong daylight
or with weak tungsten light.
Thus the Rλvalues are independent of
the actual light source used in the spectrophotometer.
.
3
4. Measured Reflectance Rλ
The actual amount of light reflected will be
different for different light sources,
however.
Suppose that the sample is now viewed
under a light source
for which the light emitted at each wavelength is Eλ.
Then the amount reflected at each wavelength will be
Eλ x Rλ.
Now if we consider only light of wavelength l, one unit of
energy of l can be matched by an additive mixture of x–
l units of [X] together with y–
l units of [Y] and z–
l
units of [Z] (Eqn 3.8):
.
4
5. Measured Reflectance Rλ
Then the amount reflected at each wavelength will be
Eλ x Rλ.
Now if we consider only light of wavelength λ,
one unit of energy of λ can be matched by
an additive mixture of
xλ units of [X]
together with yλ units of [Y]
and z–λ units of [Z]
(Eqn 3.8):
5
6. Measured Reflectance Rλ
Then the amount reflected at each wavelength will be
Eλ x Rλ.
It also follows from the properties of additive mixtures of lights that
the light reflected at two wavelengths
λ1 and λ2,
Eλ1 Rλ1 [λ1] + Eλ2 Rλ2 [λ2]
can be matched by
6
7. Measured Reflectance Rλ
Then the amount reflected at each wavelength will be
Eλ x Rλ.
The total amount of energy reflected over the visible
spectrum is
the sum of the amounts reflected at each wavelength.
This can be represented quite simply mathematically (Eqn 3.10):
where the sigma sign (Σ) means that the Eλ x Rλ. values for each wavelength
through the visible region should be added together,
and the limits of λ = 380 and 760 nm are the
boundaries of the visible region.
7
8. Measured Reflectance Rλ
The total amount of energy reflected over the visible
spectrum is
the sum of the amounts reflected at each wavelength.
This can be represented quite simply mathematically (Eqn 3.10):
Strictly the spectrum should be divided into
Infinitesimally small wavelength intervals (dλ) and the total amount of light
given
but in practice the summation form is used.
Representing the amounts of [X], [Y] and [Z] in a similar manner,
the light reflected from our paint surface can be matched by Eqn 3.12:
8
9. Measured Reflectance Rλ
Since the light reflected
from our paint sample
can also be matched
by
X[X] + Y[Y] + Z[Z],
it follows (Eqn 3.13):
9
12. Reflectance CALCULATION
The calculation can be illustrated by reference to
Figure 3.5.
Suppose we have
measured the reflectance curve
of a sample
and obtained the results shown in Figure
3.5(a).
The R values indicate
the fraction of light reflected by the sample at each wavelength.
At the wavelengths around 500 nm the sample is reflecting
a high proportion of the light that is shone on it,
no matter how much or how little light that may be.
Similarly the fraction reflected at 600–700 nm is low,
again irrespective of the amount of light shone on to the surface.
To calculate how much light is actually reflected, we need to know
how much light is shone on the surface.
12
13. Reflectance CALCULATION
Suppose that the surface is illuminated by a source
whose energy distribution is
shown in Figure 3.5(b),
i.e. the source contains
relatively less energy at the short-wavelength
end of the visible region
and relatively much more at the longer wavelengths.
The amount of light reflected by the sample
at each wavelength
will be EλRλ
and this is also plotted against wavelength in Figure 3.5(b).
We can see that while the curve resembles the Rλ curve,
with a maximum at 540 nm
and a minimum at 680 nm,
the balance between the longer and shorter wavelengths is quite different.
The R values are roughly the same at 400 and 620 nm,
While the EλRλ value at 620 nm is almost ten times the corresponding value at 400 nm.
13
14. Reflectance CALCULATION
There are two quite distinct parts
to the curve
with maxima
around 460 and 600 nm,
but the relative sizes of the two
peaks have changed.
Again the curves roughly resemble the
but the relative sizes have changed.
14
15. curves are proportional to
the X, Y and Z tristimulus values
respectively.
It is obvious that Z is considerably
smaller than X or Y.
(In fact the Eλ curve corresponds to
tungsten light
and the approximate
tristimulus values are
X = 38, Y = 45 and Z = 21.)
We can now see
why the standard observer is so
important, Provided that we know
the energy distribution of the light source
and how the tristimulus values can be under which the specification of our paint sample is
obtained without actually required,
producing a visual match for our colour.
15