I'm restoring a portrait of Edmund Holland that was painted in 1895. This painting is an oil on canvas, and it is in a painted and gilt wood frame. Both the painting and the frame are extremely dirty.

Image caption, Noon, or The Siesta, After Millet, Vincent Van Gogh, 1890, oil on canvas (Peter Horree / Alamy Stock Photo) Applying thick areas of paint on a canvas like this is known as impasto.