Local colours are composed of the general elementary colours; but these are determined or specified according to the properties of substances and surfaces on which they appear: this specification is infinite.
Thus, there is at once a great difference between silk and wool similarly dyed. Every kind of preparation and texture produces corresponding modifications. Roughness, smoothness, polish, all are to be considered.
It is therefore one of the pernicious prejudices of art that the skilful painter must never attend to the material of draperies, but always represent, as it were, only abstract folds. Is not all characteristic variety thus done away with, and is the portrait of Leo X. less excellent because velvet, satin, and moreen, are imitated in their relative effect?
In the productions of nature, colours appear more or less modified, specified, even individualised: this may be readily observed in minerals and plants, in the feathers of birds and the skins of beasts.
The chief art of the painter is always to imitate the actual appearance of the definite hue, doing away with the recollection of the elementary ingredients of colour. This difficulty is in no instance greater than in the imitation of the surface of the human figure.