In her own words...
One way to write a secret language is to employ familiar signs, obvious and unequivocal to the human eye. For this reason I chose a brilliant fidelity to the visual object as my method in painting Birthday. The result is a portrait of myself, precise and unmistakable to the onlooker. But what is a portrait? Is it mystery and revelation, conscious and unconscious, poetry and madness? Is it an angel, a demon, a hero, a child-eater, a ruin, a romantic, a monster, a whore? Is it a miracle or a poison? I believe that a portrait, particularly a self-portrait, should be somehow, all of these things and many more, recorded in a secret language clad in the honesty and innocence of paint. — Dorothea Tanning, 1943