This is one of the great portraits. Jan Six, 1618-1700, stands in utter darkness, a glowing presence emerging from an enveloping umber-black background, his wide-brimmed, high-crowned, typically Dutch hat barely black enough to differentiate itself from his dark surroundings. The cloak is red, the tunic an off-blue, the buttons, sleeves and gloves gold or golden-brown, the face warm, the collar of the cloak and frontal decorative striations golden-red, freely indicated by Rembrandt's deftly accurate brush.
There has never been a better piece of painting in the history of the world than Rembrandt's bravura handling of the gloves, hands and cuffs of the sleeves of Jan Six, to say nothing of the rest of the painting. Painterly looseness combines with careful attention to detail in the face to construct forms that are solid, structural, tangible; cursorily brilliant; real; magnificent statements of the significant use of paint. This painting epitomizes the dual riches of great art: profound content and magnificent aesthetics.
Jan Six is depicted pulling on or pulling off a glove, as if he has just arrived at his friend Rembrandt's studio, or is just departing. Surprisingly, as will be seen, the hands and gloves are the most important parts of the painting -- visually and expressively -- more so, even, than the head – which seems odd to say -- though the head is solidly painted, with more nuanced subtleties of modeling than the brash hands and gloves. Our attention is drawn to the hands and gloves by their dramatic interaction and presentation in front of Six's body, their strong contrasts of light and dark, and freedom of paint application. Six's face is less dominant because it is darker than the lighter bare hand and white cuffs, with much less contrast of tonal values. The painting becomes, therefore – as unusual as it may sound – a portrait of hands and gloves, and all that the process of "putting on/taking off" implies...rather than strictly a portrait of Jan Six, though it is, indeed, a superb one.
The character and feeling in the face of Jan Six is resonant and profound, sensitive and thoughtful; and, as in most of Rembrandt's portraits, he is seemingly very aware of life, its brevity, ambiguities, beauties, pains. The profound thoughtfulness and insight expressed in Six's eyes, mouth and general feeling in his face, also reflect Six's awareness of the meanings Rembrandt has constructed in his hands and gloves, made vital and extraordinarily alive by the brilliance of flashing brushwork.
... The portrait of "Jan Six"...and his hands...is at least as mysterious as Leonardo da Vinci's famously mysterious "Mona Lisa"...with her smile.
See also https://en.wikipedia.org/wiki/Portrait_of_Jan_Six