Series editors' preface - Wood Tools

Table 5.3 Pigments – continued
Other materials and structures 225
Colour/group Chemical composition Origin/date Properties Refractive
Pigment and description Index
name
Hansa
yellow
Naples
yellow
Chrome
yellow
Barium
yellow
(Lemon
yellow)
Strontium
yellow
Cobalt
yellow
(Aureolin)
Cadmium
yellow
Gamboge
brown and violet. Very
homogeneous and fine but with no
significant advantages over natural
yellow and red counterparts
Permanent greenish yellow lake
pigment made by precipitating one
of a range of Hansa yellow dyes
on an inert base. The dye is
prepared from diazotized aromatic
amines containing nitro or halogen
groups coupled with acetoacetanilide
or its derivatives
Lead antimonate (Pb 3(SbO 4) 2).
Varies from yellow to orange
depending on the proportions of
the oxides of lead and antimony
chemically combined in the
compound. Homogeneous, finely
divided like massicot in appearance
Lead chromate (PbCrO 4). Usually
very fine rather opaque crystals
varying in colour from lemon
yellow to orange depending on
particle size and conditions of
preparation
Barium chromate (BaCrO 4). Dull,
pale, greenish yellow by reflected
light but nearly colourless in
transmitted light. Very fine
crystalline or plate form
Strontium chromate (SrCrO 4). Mass
of finely divided needle-like
crystals. Deeper and brighter than
barium chromate, also sold as
lemon yellow
Complex compound – potassium
cobaltinitrite (CoK 3(NO 2) 6.H 2O).
Tiny crystals and crystal clusters,
yellow by transmitted light
Cadmium sulphide (CdS).
Depending on the conditions of
preparation, precipitated cadmium
sulphide varies from lemon yellow
to deep orange. Colour differences
depend on the size and state of
crystallinity of the pigment particles
but all types are comparatively
finely divided
Yellow resin produced by trees of
the genus Garcinia. Used with
indigo or Prussian blue as
component of Hooker’s green
Recipes for this pigment
appear from the mid
eighteenth century but a
similar material was in
use much earlier. Name
now used to indicate
shade of yellow rather
than a specific
compound
Preparation described in
1809. Commercially
available from c.1818.
Commercially important
pigment. Expensive
Discovered in 1848 and
first used as a pigment
in 1861. Expensive
Found as a mineral in
nature but that used for
pigments is precipitated
from an acid solution of
a soluble cadmium salt
by the action of an
alkaline sulphide or
hydrogen sulphide gas.
First used in 1829
commercially available
from 1846
Good hiding power. Lightfast.
Suitable for artists use.
Good hiding power. Chemically
stable but is darkened by hydrogen
sulphide and is therefore more
used in oil than in water based
media
Pure lead chromate is fairly stable
to light but may darken and
become brown on ageing. May
become green (by reduction to
chromic oxide) in mixtures with
organic pigments. Best used in oil
Poor hiding power. Most stable of
the chromate pigments. Soluble in
dilute alkalis and mineral acids.
Little affected by light but may
become more greenish in strong
light due to chromic oxide
formation
Greater hiding power than barium
chromate
Fair hiding power. Light fast but
impure samples unstable. May
accelerate fading of organic
pigments itself turning brown in
the process. Decomposed by
strong alkalis and acids, slightly
soluble in cold water
High refractive index and therefore
good hiding power. Permanent and
fast to light. A very important
yellow pigment. Toxic
Used mainly in watercolour or in
varnish. Permanent in oil but less
so in watercolour when it fades in
strong light
2.01–2.88
2.31–2.49
1.94–1.98
1.92–2.01
1.72–1.76
2.35–2.48
1.58–1.59
continued