Mating two pieces When it's time to fit a newly
fashioned piece of marble with a broken or irregularly shaped ancient one, the
team once again borrows from Periclean times. To ensure that the new piece
exactly snuggles against the old, they coat the inner surface of the new marble
with red clay. They gently push the two pieces together, then pull them apart.
Points on the new piece that turn white—that is, where the clay is
scraped off—indicate spots on the new slab that need fine-tuning. The
operation is repeated dozens of times until the new marble precisely matches
the ancient surface.