From the “Handbook of Construction Techniques” about in 1960

Keeping a Cool Head

After experiencing severe headaches for several days while wearing his metal safety helmet in the hot sun, Ray Vaught, a foreman with E. E. Barber & Sons of Texarkana, Ark., came up with a cool idea to take the heat off his head. He put a 1-ft-square piece of 3/16-in.-thick asbestos inside his helmet as an insulator.

The marked difference in temperature between a lined and unlined helmet was clearly evident by touch. By strapping a thermometer inside an asbestos-lined helmet, Ray found that the temperature inside was as much as 20 deg cooler than the temperature outside. It wasn’t long before everyone on the job had adopted his idea for keeping a cool head.