Metal grains dye fabrics in muted hues.

Mere mortals may not be able to afford garments made of spun gold, but a new fabric-dyeing process offers humble folk a less costly alternative. By bonding tiny particles of gold and other metals to cloth fibers, William J. Todd of Louisiana State University in Baton Rouge can tint fabrics with a range of colors.

The hues achieved by this process evoke a misty meadow rather than the shiny lame costume of a Las Vegas entertainer. Gold grains turn fabric pink or red, and other metals look yellow, green, gray, and tan, Todd says. The nanometer-size particles scatter light in such a way that the material takes on those various colors (SN: 10/3/98, p. 216).

To dye a piece of fabric, Todd soaks the fibers in a solution of metal ions. The ions cluster around the fibers and react to form solid particles that adhere to the threads. Unlike organic dyes, the metal grains don't wash out or fade in the sun, he says.

Although the technique sounds expensive, not much metal is needed to dye fabric. "We work with very dilute solutions that have an ion concentration of about one-hundredth of one percent," Todd says. He estimates that 1 ounce of gold would color about 380 miles of spun viscose yarn.