Laymen and beginner painters generally think of paints primarily as colors. Theoretically a painter ought to have on his palette a series of evenly staggered paints that would allow to reproduce any color he might see in nature. Nothing could be farther from a real-life working palette of the seventeenth-century painter.
Except in specialist art conservation literature, seventeenth-century pigments—pigment is the coloring substance of paint—are discussed in very general terms and it is not always realized that painters of those days were influenced as much by their cost, availability and behavior as their aesthetic qualities. The infinite number of near-monochrome dank tavern scenes, which had literally inundated the Dutch art market, must have owed something to the fact the earth pigments used to make them were the cheapest and easiest to handle of all pigments, available to seasoned masters and lowliest untrained "gallery slaves" trying to eke out a better living that of the dock worker.
Even Vermeer, supported economically by his patron Pieter van Ruijven at least in part, was influenced by the monetary value of his pigments. It can be legitimately questioned if the artist's almost obsessive proclivity for the finest variety of natural ultramarine owed only the pigment's brilliance, or equally, to its elevated costs and noble pedigree that would have enhanced the value of his painting in the eyes of potential buyers.
It is almost certain that any painter or art lover of the period would have immediately grasped that the magnificent Woman in Blue Reading a Letter was for all practical purposes an exercise in the costly ultramarine: not only is natural ultramarine present in the striking morning jacket, but in the deep blue tablecloth, the chairs' upholstery, the rolin bar of the map, the shadows cast on the wall and even the white wall itself
Some paints, like the earth pigments and the touchstone lead white, could be employed indiscriminately. Others, like weld, a yellow lake made from the rocket flowers, had to managed with care. It was yes particularly adapted glazing due to its high transparency, but it was notoriously apt to fade. Smalt, a cheap and readily available blue made of cobalt ore heated with glass, was most effective when tempered with fast-drying glue medium since its coarse particles are so heavy that they sink in under essential oils oil and become dull or worse, slide down the canvas when set vertically on the easel. In fact, smalt was generally used as a cheap base for more expensive blues or as an admixture to accelerate drying time of slow drying paints..
Vermeer's lovely morning have a curious lemon yellow hue not only because the color attracted him or because they were indeed yellows as the appear in his paintings, but because lead-tin yellow was the only strong that unquestionably did not fade, an issue which was doubly important in deciding the color for prominent passages. Moreover, it was recommended to employ it unadulterated or mixed with pure white for the illuminate passages. Adding of other pigments to alter its tone and would have appreciably lowered its already limited brilliance. Few viewers have an idea of how dull Vermeer's lead-tine yellow pigment appears when it is set aside of any of today's cadmium yellows. Therefore, it is very probable that when Vermeer, like all painters, set out his palette for the day's work, he though as much in terms of available pigments, their technical limitations and handling behavior than in terms of color. Color may even be a secondary question.