As it dries out during frying, the chip shrinks. Minimizing its area, it curls into a saddle shape. Every little section of the Costa surface has this saddle configuration. Indeed, one can imagine the surface as the sum of an infinite number of saddles. From certain angles, the Costa surface has the splendid elegance of a gracefully spinning dancer flinging out her full skirt so that it whirls parallel to the ground.
Gentle waves undulate along the skirt's hem.
Two holes pierce the skirt's lower surface and join to form a tunnel that sweeps upward. Another pair of holes, set a right angles to the first pair, lead from the top of the skirt downward into a second tunnel. An image of the Costa surface generated using Mathematica. Several years ago, Ferguson created a number of marble and bronze versions of the Costa surface. Carving one in snow, however, presented a host of new challenges.