Underpainting/Overpainting Portrait

Today, I began to add color over the underpainting of a woman.The left photo shows the purplish brown glaze(thin transparent paint) applied over the red and white underpainting. The photo on the right shows the portrait 90% completed, opaque oil paint applied in the areas the the light has touched the face. I leave the glaze paint in the shadows untouched. This technique causes the light to