One of Rembrandt's pupils, Samuel van Hoogstraten, wrote a book of art theory in which many of Rembrandt's instructions to his students are apparently echoed or repeated. Among them is a recommendation that the painter, making a rough sketch, might look at his model with half-closed eyes in order to eliminate distracting details, and to indicate (as Otto Benesch has paraphrased it) "with loose strokes and touches the hollow shadows of eyes, nose and mouth."
Such a technique, epitomized in the mastery and ease of this brush-and-ink drawing of a sleeping girl, can therefore be said to be a fully conscious method of depicting subjects freely and boldly, of deliberately losing small details in a larger conception -- of catching and recording only the essentials of form played over by light and shadow. What could possibly be a more appropriate way of drawing the naturalness and ease of sleep?
This drawing reveals the mature self-confidence of a great painter. But it is interesting that Rembrandt is known by report to have been a thoughtful and not particularly quick worker. Most of his paintings show this: they don't display bravura so much as the steady building of an image in gentle and rich gradations of deep shadow and powerful light. The substantiality of their paint-surface is composed as thick dabs and deposits of paint rather than as fluid gestures. A comparison with Frans Hals is telling in this respect.
There are exceptions, however, -- one being the panel in London's National Gallery of "A Woman Bathing," dated either 1654 or 1655. The "Sleeping Girl" drawing is thought to be approximately the same date, and both usually carry the parenthetical label of "Hendrickje Stoffels?" The way in which Rembrandt painted the girl's shift in "A Woman Bathing" comes close, in its boldness and freedom, to his treatment of the folds of her dress in "A Sleeping Girl." The style of hair, the shape of her head, also seem similar. Whoever she is, it seems more than likely the same person.
But neither is really a portrait. Instead, Rembrandt was evidently using her as a model (though obviously delighting in her form) and both figures seem far more universal than particular. They enter the classicism of his late vision, and the comparatively uncareful execution of both these works (it is intriguing to be able, in this case, to compare a drawing and a painting) does not result in figures that are less monumental than before. Indeed this looseness effectively subserves their structure. Freedom of technique hasn't resulted in some kind of painterly brilliance -- clever style for its own sake. It is a matter-of-fact method of representing the subject.
The fall of light and the trapped and infolded shadows are of as much interest to the artist in his "Sleeping Girl" as the figure itself. The marvel is that this contrast of dark and light, translated into the blot and stroke of tonal ink-washes on paper, is so entirely appropriate to the subject. Some writers have seen Rembrandt's drawing as a kind of shorthand: for his information rather than ours. Himself a great collector of artists' drawings, he was well aware of the self-sufficient value of expressive drawings. His own speak with considerable force and directness. Their very lack of scrupulous finish contributes to this, and Rembrandt surely knew it. For all its "sketchiness" the "Sleeping Girl" has its own completeness: enormous experience informs both the spontaneity of its observation and the swift assurance of its draughtsmanship. But here is the visual language of practicality and not the charming dexterity of a traditional artistic skill, like the "brushwork" of some Japanese or Chinese scrollpainter. It is altogether too untidym a work for it to be seen as a westernized sport from the Orient.