It is a substance (pure pigment) or preparation (compound pigment) in the form of practically insoluble fine particles, unlike the dyes which are in liquid solution (dye for ink, for paint, for dyeing ...)
Mineral pigments, organic pigments and metallic pigments can be found.
They can be "natural", which is the case of ocher, land, which is in the natural state, and undergo only a process of calcination and / or mixtures.
Or "synthetic" obtained by thermal and / or chemical reaction between several materials. We are talking here about "green chemistry". Their hues are less dull than that of natural mineral pigments.
Average characteristics of mineral pigments:
- Excellent resistance to light and weather
- high resistance to water, acids, alkalis
- good coloring power
- high coverage
- better resistance to chalking
Nowadays, organic pigments are essentially azo pigments (yellow, green, purple), phthalocyanines (blue, green) and quinacridones (red, purple)
They have a greater coloring power than mineral pigments, but are often more transparent.
Their behavior in the light is average.
The metallic pigments are metals or alloys in the form of powders, obtained by spraying or by chemical precipitation.
They are mainly used in creative leisure.
A "pure" pigment consists of a single chemical compound (yellow ocher, red ocher, its natural). A compound pigment is a pigment obtained by combining several "pure" pigments, natural or synthetic.
For the names of the colors used by the manufacturers, of strict controlled label of origin, for example, under the name "Earth of Siena", one can find: a natural ground extracted near Siena, simply ground and sieved, a natural earth of another origin having a tone and a similar chemical composition or a mixture of different natural materials.
We can also find a cinnabar, which is normally a sulphide of mercury, made from a combination of synthetic pigments whose tone is close to the real cinnabar.
It is therefore important to refer to the references in the Color Index, which lists thousands of pigments, dyes and fillers. These references include letters and numbers:
First letter: P for pigment
A second letter (and third letter for some):
W White (blanc)
Bk Black (noir)
R Red (rouge)
Y Yellow (jaune)
B Blue (bleu)
O Orange (orange)
G Green (vert)
Br Brown (brun)
A number from 1 to 3 digits corresponding to the category of the pigment
It is the property of maintaining the intensity of the coloration after prolonged exposures to light. Natural mineral pigments have the best UV stability
It is the ability of a pigment to communicate its own color to a medium or a pigment mixture. Some organic pigments color twice as much as mineral pigments.
The hiding power (or opacifying power) of a pigment in a binder and for a given concentration is measured by its ability to cover the surface of a support with two contrasting areas: black and white.
We will speak of "opaque pigments" or "transparent pigments", but the fineness of the grinding also has a great influence on the covering power, as well as the pigment / binder dosage. Transparent pigments will be interesting for oil glazes. Organic pigments are rather transparent whereas mineral pigments are generally more opaque.
It is the ability of a pigment to accelerate the drying of the oil used as a binder. This criterion is important especially in the choice of grinding oils and mediums. A pigment may contain mineral compounds with a drying action, while some pigments may delay drying.
The list established with respect to linseed oil is as follows
Among the very drying pigments: manganese pigments
Among the siccative pigments: red, yellow or black iron oxides,
Among the low drying pigments: ultramarine pigments, green lands
Among the pigments retarding drying: calcination black
The company OCRES DE FRANCE has selected a range of pigments that is safe for humans and the environment.
However, pulverulent materials alone constitute a danger simply because of the fineness of the particles that can be easily inhaled. We recommend wearing a mask when handling pigments and keep them out of the reach of children.