Pareles Bros., Inc., a Milwaukee, Wisconsin custom molder, patented a process in the mid-1940s for injection molding of cellulose acetate around a wooden core to create brightly colored, protected and easily washable heels for women's shoes. The plastic material was slightly impregnated into the wood under pressure of injection. The resulting heel appeared all of a piece, with no seam, and without the scratching, chipping and peeling that was previosuly common with painted wooden heels.

Pereles Bros. also developed and injeciton molded a variety of drafting instruments including slide rules, flat four-bevel engineering and architectural scales, half-round protractors and other items. Injection molded thermoplastic replaced traditional metal and boxwood which became difficult to obtain during World War II. In order ot ensure accuracy, Perles installed its own engraving department to create the hundreds of measured lines needed in the dies.

See:

"Accurate Drafting Instruments," Modern Plastics, 32:2 (Oct. 1944), 114, 194.

"In Step wiith Fashion," Modern Plastics, 32:3 (Nov. 1944), 114-155, 206.