Van Dyck appears increasingly ill-at-ease, as if his fierce concentration on the task at hand has been diverted by some unexpected intrusion. He seems startled, and I can imagine him feeling annoyed by the disturbance. His mouth might be on the point of opening. A hint of a frown can be detected curving up from the edge of his raised right eyebrow.
What is really going on here? Van Dyck's last "Self-Portrait" may well reflect his gathering alarm about the state of his adopted home. Charles I, who contributed so greatly to Van Dyck's success, had alienated a growing number of powerful forces. And Van Dyck's eminent position within the royal court must have alerted him to the danger now confronting the monarch. (Civil war would break out in 1642.) Van Dyck was sensitive enough to appreciate the problem, and his anxiety could have been exacerbated by his own illness.
Van Dyck probably sensed, when he stared at his own reflection and set it down on canvas, that his health was ominously poor. In August 1641 the Countess of Roxburghe reported in a letter that he had been ill for a long time, and soon afterward Van Dyck grew so infirm that he abandoned a major commission to paint Cardinal Richelieu's portrait in Paris. He must have felt very frustrated, and at the base of the elaborate oak frame surrounding his last "Self-Portrait" a demonic face scowls as he opens his mouth in a roar of rage. There is certainly a haunting awareness of transience in the "Self-Portrait." Even as he emphasizes the strength of his penetrating gaze, Van Dyck conveys a melancholy awareness that nothing of him will endure very long, apart from the art he creates. The white shirt that occupies such a prominent space near the center of the painting looks as turbulent as a storm-stricken sea. This boldly handled passage of paint could almost be seen as prophetic, hinting at the military tempest that was about to engulf England and destroy the king along with so many of his subjects in a catastrophic conflict.
The National Portrait Gallery in London is raising funds to purchase, preserve, and display this portrait (and keep it from being obtained by a private collector). More about that effort here.