The question of when a painting is finished is difficult to answer.
Throughout the history of art, questions of completion depended upon in what period one was painting.
In the 17th century, for example, a painting was finished when the narrative was firmly in place, the surface of the painting was taut and glazed, and when little was left to the eye and the mind to question. Most of the work was done by the artist.
Picasso and others in the beginning of the twentieth century began to question ideas about finish and levels of completion. Picasso opened the door to leaving a painting with a kind of fresh composition and surface that went against early notions of finish and completion. Picasso played with the surface and attendant mark making. He might leave areas of the canvas exposed. In other cases he changed direction often with the mark of the brush and changed again and again so that the viewer is pulled into a tangled web of decision and indecision.
For me, a painting is not so much finished as left alone after several or many approaches in the “battlefield” of the studio. For me, a painting develops. After a certain point, it takes on a life of its own and this energy speaks back to me as the painting progresses. This pushing back on the artist is a very good thing.
I work the canvas on the floor of the studio, moving around and around the painting, losing sight of up and down, left and right or east and west. Getting lost in the canvas allows the free brushwork and play of a child who is not thinking of a certain result but rather is luxuriating in the delight of what a loaded brush of liquid paint can achieve on a fresh surface.
After a time I hang the painting on the studio wall and make necessary changes and revisions.
A painting is finished when it does not answer all the questions. A painting is finished when it is strong enough to go out in this world on its own.