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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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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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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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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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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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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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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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