Bamboo sheets are sold as the gentle alternative to cotton and silk, and the fabric they are made of is the one that put factory workers in asylums. Bamboo cloth is not bamboo. It is viscose. The plant is pulped, dissolved in caustic soda and carbon disulphide, and squirted through a nozzle into acid, where it sets into a thread. It was patented in England in 1892 as artificial silk, and the trade name for it was rayon. The same process makes a kitchen sponge and the cellophane on a bunch of flowers. Carbon disulphide was already notorious. French doctors in the 1850s had watched it send rubber workers blind, impotent and insane. The viscose industry needed it in enormous quantities and nothing else would do. So from the 1920s the asylums began to fill. In 1933 a doctor at a Pennsylvania rayon plant wired Alice Hamilton, the first woman on the Harvard faculty and the country's authority on industrial poisons, with a 6-word message: an epidemic of insanity has broken out. Workers were going home and attacking their wives. Men in the churn rooms were found wandering the roads. Investigators who got inside found a third of the workforce showing signs of poisoning. The companies fixed prices, sat on the evidence, and when the regulators finally came for them in the West they moved the factories to India, China and Indonesia, where the same chemical is used today. The consumer was never harmed. Only the people who made the cloth. Silk is made by a caterpillar in a mulberry tree. Wool is made by a sheep in a field. Both are a protein, same as your own hair, and both have been pulled off the animal for 5,000 years without sending anybody out of his mind. The fake silk needed a chemical that could not be made safe, and the industry's answer was to make it somewhere else.