Rainbow Bits

Report by George W. Hart

February 1999


Object name: Rainbow Bits

Creator: George W. Hart

Completed: 21 February 1999

Location: Components (prepared in Northport, NY) were assembled on site in Soda Hall, U.C. Berkeley, Berkeley, CA.

Size: 100 inch total height, including 77 inch diameter sphere and supporting mount.

Material: 642 slit CDs.

Support: 10 fiberglass rods, oak hub, stainless steel wire and hooks, silver crimps, assorted hardware (screw eyes, washers, nuts, connectors). White flat finish latex/acrylic paint on hub; white flat finish enamel spray paint on rods.

Description: Rainbow Bits is a suspended assemblage of CDs connected into arcs outlining a spherical form. The CDs have a holographic front surface, which provides strongly colored rainbow effects in addition to the usual diffraction effects of the information-carrying surface. The disks have been slit and slid into each other to make the mechanical connections, and welded with solvent cement.

Wires to a spider-shaped overhead support distribute the load over thirty-two disks. The top and bottom disks are wired with a screw eye and washer assemblage, and thirty other disks are wired via a hook in their central opening. The wires loop around the fiberglass rods and are fastened with a crimp. The rods are friction fit into holes drilled in the central hub, from which the entire sculpture is suspended and free to rotate.

Design: The 642 CDs follow the edges of a polyhedron tentatively called the "canonical propellorized icosahedron," which consists of twenty equilateral triangles and sixty kite-shaped quadrilaterals, arranged with icosahedral symmetry. The form is original to the sculptor, i.e., the polyhedron is not previously described in the mathematics literature. The quadrilaterals have the special property of being "triequiangular kites" meaning that two pairs of edges have equal lengths and three angles are equal. (A paper model of the polyhedral form was provided with the sculpture.)

Six different types of cut CDs are employed: twelve have 5 cuts, sixty have 4 cuts, and there are four different shapes with 2 cuts, making a total of 1440 cuts. The precise depths and angles of the cuts determine the final geometry. The sphere of the tangent CDs is 72 inches in diameter, and with the additional 4.75 inch diameter of CDs orthogonal to that spherical surface, the total sculpture has a 77 inch diameter. The top of the sphere hangs 20 inches below the supporting mount.

Conservation: Little maintenance other than dusting should be required. Regular visual inspection for disconnected support wires, broken disks, or other damage is recommended. Acrylic plastic CDs are brittle, so physical contact should be minimized.

Presentation: Spot lighting is recommended to bring out the color.