This is Picasso’s shopping list in the fascinating description by Brassaï . In fact, what is essential to the painter is the colour or – technically – the pigment, a matter with required special features.
First of all the artist, no matter the period he lives in, must consider the hue he wants to achieve. The range is more or less extended, depending on the Age: may he find raw materials in loco or import them? Which kind of recipes the atelier prefers? Can he use synthetic pigments or shall they be still discovered?
The skilled painter also knows the more suitable substance for the chosen support – panel, canvas or wall.
Some pigments are not compatible with the fresco technique, that is with the plaster: cinnabar or azurite, for example, are respectively red and blue pigments that can only be applied “a secco”. This means that the painter must wait for the plaster to be dry before applying water as additive.
Only in the last century artists have become aware of pigments toxicity. Mental and physiological diseases, more or less known for famous painters like Caravaggio or Van Gogh, may derive from lead poisoning, as lead was a primary elements in the pigments they used – white lead and Naples yellow.
Moreover, the coast itself is a parameter in the choise of a pigment. That is why in Medioeval Age contracts have been stipulated between a client and an atelier, specifying the pigments, their quality and usage. It is not a legend that the precious ultramarine blue could not be mixed with others, unless being charged with blasphemy.
The farthest the pigment was, the most it coast. This is true for inorganic pigments, that is mineral extracted from far quarries, but also for the organic ones, from exotic plants and insects, called laque. For both of these categories a synthetic path is known, so that they can be artificially produced in factories.
We will now move through a paint-journey in which, no matter what the pigment is, the first astonishing thing is the human need, conscious or not, of leaving his own mark, with new and more complex materials and techniques.
 Brassaï, Conversations avec Picasso, Paris (1964); trad. it. Conversazioni con Picasso, Allemandi, Torino 1996.