Series editors' preface - Wood Tools

diffraction, energy dispersive X-ray fluorescence
spectrometry (ED–XRF), in further determining
the stone’s composition (Johnson and
Maxwell, 1981; Lazzarini et al., 1980; McMillan
and Hofmeister, 1988).
Fraquet (1987) and Rice (1980) describe the
physical and chemical characteristics of different
ambers and give a general gemological test
for their identification. Methods for determining
the provenance of amber are discussed by
Beck (1982).
5.8 Colorants: pigments, dyes and
stains
A wide range of materials of very diverse
origins and chemical types has been used to
colour wood and other materials found in
furniture. Pigments and dyes may be classified
in a variety of ways according to their colour,
origins, historical availability, chemistry, physical
properties and permanence. Stains constitute
such a diverse group that it may be more
productive to consider them from the point of
view of the medium in which they are used.
This subsection discusses in a general way the
terminology associated with this functional
group of materials and is intended to be illustrative
rather than exhaustive. There is an
extensive and excellent literature on the
history, variety, chemistry and use of pigments
and dyes and the reader is referred to sources
listed in the bibliography. For further information
on pigments see Feller (1986), Gettens
and Stout (1966), Harley (1982) and Mayer
(1982). For further information on dyes see
Abrahart (1977), Liles (1990) and sources listed
in Chapter 3. For further information on other
colorants used on furniture and woodwork see
Hayward (1974), Sheraton (1803), Siddons
(1830) and Stalker and Parker (1688).
5.8.1 Colour
The sensation of colour arises through the
influence of electromagnetic radiation of
wavelength 400–700 nm on the human eye.
The chromatic quality or hue of a colour is
indicated by name as red, orange, yellow etc.
Value describes the relationship of a colour to
white and black. Higher values of a colour are
lighter and lower values are darker (this is
Other materials and structures 219
equivalent to a physicist’s brightness of light).
To change the value of a colour we can mix
it with something lighter or darker. Adding
black or white changes the value but does not
change the hue. The intensity of a colour is
the strength of hue as compared to a colourless
neutral grey. This is well illustrated by the
comparative terms brilliant and dull. Other
terms used to describe intensity of pigment
colours are saturation, chroma, purity, vividness
and brightness. Intensity is reduced by
mixing with another colour. It is possible to
change the intensity of a colour without
changing its value or hue by adding neutral
grey of the same value.
Because there are three independent
variables of perceived colour, it is impossible
to achieve a logical arrangement in two
dimensions (on a paint card for example).
Consequently, various systems have been
developed to describe or map colour space
in three dimensions. Perhaps the most well
known of these is the Munsell system. The
Munsell system suffers from the disadvantages
that colour chips on adjacent plates show large
hue differences at high chroma but very small
hue differences at low chroma. Also, there are
too few chips for the high chroma colours
which (at least industrially) are more important.
To cope with these difficulties, the
Munsell system, with 1488 glossy colour chips
and 1277 matte chips, has been expanded by
the Japanese Chroma Cosmos system which
has 5000 colour chips. Other colour atlases
have also been developed including the
Optical Society of America OSA-UCS system,
the Natural Colour System and the ICI Colour
Atlas which illustrates 27 000 different colours
(McLaren, 1983). For everyday purposes, the
Methuen Handbook of Colour (Kornerup and
Wanscher, 1978) provides a useful way to
compare and describe colours.
Why objects appear coloured
Light of different wavelengths falling on the
retina of the eye gives rise to the sensation of
colour through the response of the cones in
the retina (Gregory, 1966). Light of wavelength
400 nm gives rise to the sensation of blue
and that at 700 nm to red. A mixture of all
wavelengths appears white. When white light
hits a surface it may be reflected, transmitted
through the object, or absorbed. If all light is