In this (one in a frequent series), Emma Pearce (Educational and Technical
Services Manager for Winsor & Newton) discusses watercolour pigments:
"Aside from hue, the choice and use of different watercolours depends of
three further areas: transparency, granulation and staining. This article
classifies (them) by these characteristics. The permanence of watercolours
is also worth a special mention."
She goes on to give a brief definition of the areas. Granulation adds visual
texture as the pigment particles tend to settle in the hollows of the paper.
In general she states that traditional pigments granulate whereas modern
organics do not, The tendency to granulation is reduces by using distilled
water in hard water areas.
Also in general terms, the modern organics have finer particles which cause
them to stain.
On permanence she comments "There are no colours listed in these tables
which are anything less than permanent."
She then gives 4 tables listing: Opaque or semi-transparent colours,
granulating colours, transparent or semi-transparent colours and staining
colours, giving the colour name and the Colour Index Generic Name. Of course
colours may appear in more than one of these.
On colour names she comments that "manufacturers do not necessarily use the
same pigments, so common names alone may not reflect the characteristics in
the table. I have listed the most common watercolours to minimise any
differences."
Peter Marshall
On Fixing Shadows, Dragonfire and elsewhere:
http://faraday.clas.virginia.edu/~ds8s/
Family Pictures & Gay Pride: http://www.dragonfire.net/~gallery/
and: http://www.speltlib.demon.co.uk/