Rembrandt van Rijn was born in Leydn, and later moved to Amsterdam to study in the studio of Peter Lastman. Lastman, who had traveled to Italy and was familiar with the works of Carravagio, likely instilled a love of chiaroscuro in the young Rembrandt. Rembrandt's early paintings, however, were done in the Dutch seventeenth-century style, consisting of thin layers.
With age came the development of Rembrandt's signature style. His use of impasto in the light areas grew heavier and heavier, while his shadows became increasingly transparent. His series of self-portraits document the evolution of his technique, offering an invaluable glimpse at the growth of a true 'Master'.
Rembrandt's medium seems to have been a very thick jelly that became tacky relatively quickly, judging from the light areas in his paintings. It's clear that the paint was put down and then moved around with great difficulty, producing his distinctive brush-strokes. The shadows, transparent with dark tints of color, are equally thick, the brush-strokes standing in high relief. There is some question as to Rembrandt's talent for drawing, as he seems to have been correcting his drawings after the paint had already begun to resist the commands of his brush.
Despite the existence of some alla prima sketches on panels, Rembrandt's preferred surface was a gray-toned canvas. The canvas is better suited for paintings carried out over several sittings, and the majority of Rembrandt's works were executed in this manner.
As mentioned earlier, Rembrandt did not have the gift for drawing possessed by many of his contemporaries, most notably Rubens. When painting from life, which he usually did, he needed several sittings to get the drawing up to his exacting standards. With warm brown tones of oil paint and medium, he would sketch the portrait on the canvas, blocking in the transparent shadows with the thin mix. Then, loading his brush with an opaque, muted skin tone, he painted into the light areas and modeled them with the shadows, creating powerful contrasts between the two.
Next, mixing black and white, Rembrandt created a cool gray for the mid-tones between the lights and shadows. He also used an optical gray, allowing the toned canvas to show through rather than painting in gray tones. Unfortunately, the grays in Rembrandt's paintings often appear green today, due to the yellowing varnish.
Rembrandt then worked feverishly against time and drying paint, building up the contrast between his heavy, opaque lights and his much thinner transparent shadows, as well as that of his warm and cool tones. Only when the paint became tacky and hard to move would he start the process of blending, creating the remarkable texture unique to Rembrandt's style of painting. Finally, when the paint could no longer be moved, he stopped painting and allowed the canvas to dry.
The second sitting consisted of glazing the entire surface of the canvas with medium and a tint of umber, or possibly black, which he would then carefully remove from the light areas using a cloth. The heavy impasto of the light areas retained some of the glaze, creating an even more three-dimensional appearance. This process was repeated over several sittings, resulting in the brilliant lights and darks that Rembrandt is so famously known for.