Finding shadow-hardened mainsprings can be a difficult task, but several methods can be used.
Shadow-hardened mainsprings are made of steel that has been hardened by heating it to a high temperature and then quenching it in oil. This process gives the steel a martensitic microstructure, which is very hard and wear-resistant. Shadow-hardened mainsprings are typically used in high-performance applications, such as firearms and racing engines.