This is a unique artistic genre which can tell us more about the mind of an artist than any other. Art historians and researchers have often paid considerable attention to self portraits to help fill in some of the blanks left by inconclusive documentation. Thankfully, most modern artists have a wealth of information around their lives that is freely available, but those from before the 20th century are not often as well covered. In Rothko's case there is much known about him from a variety of sources, some more reliable than others. Despite all that, however, it is still well worth looking more deeply into his particular artwork. The style here is expressive, and so this was never intended to be a precise, picture perfect representation of how he looked on that particular day.
It has been reported that Rothko had been interested in the work of Rembrandt during the 1930s and had studied much of his work across several art institutions located in New York City and elsewhere across the US. Rembrandt became one of the most prolific artists with self portraiture from any period and so this may well have influenced his decision to work in this way himself. Rembrandt found this genre would sell well in his local community and so worked hard to produce a variety of them, both oil paintings and also etchings. Someone who worked frequently in this genre but much more recently was Frida Kahlo, who gifted us the likes of The Two Fridas, The Broken Column and Self-Portrait with Thorn Necklace and Hummingbird.
Within Rothko's 1936 piece we find him staring to our left whilst wearing dark glasses. The detail is loose which makes it harder to pinpoint specific facial expressions, but the artist wanted to leave an ambiguity. He is smartly dressed with a red tie and appears to be holding one wrist with the other hand, possibly playing with a wristwatch. He has a soft looking beard and thick brown hair which has somewhat receded backwards in a uniform manner, increasing the exposure given to his forehead. There are some elements of shadowing here but the piece is highly expressive and contemporary, with the background also offering no discernible features.