The painting technique is the usual one that characterizes Vallotton: a realistic profile that is almost hard edge just to underline that particular moment and not another. The woman is undressing thinking to something else, the look is almost absent and unfocused, she looks lightly below the point of view of the observer. It is the hat to attract our attention: a large hat of deep purple color. Certainly draws attention. Maybe she will strip naked and keep her hat. The background of the painting is neutral and is only the purple to emerge, it affects the curiosity of the observer that is even distracted by the impending nakedness of the young woman. What did the artist mean? Perhaps, look at the purple hat and not the woman? Why never? Sometimes a trivial detail as a hat can become disturbing and introduce tension in the form where there should not be. But beware, only a great artist like Vallotton can do it and not anybody else.