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H20: Nature
of Light> A ray of light is a flow of energy in the
form of an electromagnetic wave. Electromagnetic waves are a special
type of oscillation in the magnetic field and the electric field. |
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H21: Light,
Materials and Colour> When we are viewing an object or
a surface, it is the light reaching our eyes that conveys the
appearance of the surface to us. The appearance is our interpretation
of the characteristics of the light, characteristics that arise from
the interactions of the light incident on the object with the material
of the object. |
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H22: Lamps
and Colour> Each type of light source provides a
different distribution of power within the spectrum. For example,
daylight has more power in the blue/green part of the spectrum than in
the orange red whereas an incandescent lamp has the reverse, more power
in the orange/red than in the blue/green wavelengths. |
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H23: Types of
Colorant> The most common mechanism of creating colour
is the selective absorption of light wavelengths, occurring in most
dyes or pigments used in creating surface colours. Examples of the use
of light absorption in creating colour might be dyed fabrics, paint
layers, pigmented plastics or printed card. |
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H24: Colorant
Properties> The optical properties of pigments are
introduced as well as the application properties. Transparency, tinting
strength, light fastness, heat fastness and weathering properties.
Chemical resistance and solvent fastness. |
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H25:
Colorants for Four Colour-Printing> By far the largest
volumes of ink are used in three and four colour sets. Because large
amounts are used annually, the cost of the inks and economy of use is a
major consideration. A standard colour, high tinctorial strength and
economy in use are vital characteristics for colorants that are
suitable for process inks. |
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H26: QC Tests
for Colorants and Inks> Pigments are used in materials
in the form of a dispersion of fine particles and the colour produced
by the dispersed pigment depends on the distribution of sizes and
shapes of the particles. It follows that the colouring properties of
pigments are best tested in the same type of material in which they are
to be used, the principle types being printing inks, paints and
plastics. |
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