Why Did Hatters Use Mercury?

Mercury was used in hat making to toughen the fur's fibers and make them mat together more efficiently. The compound used to moisten the fibers was Mercury Nitrate Hg(NO₃)₂, and the process is called carroting. It produced a superior-quality felt, which in turn, resulted in higher-quality hats.

When did hatters start using mercury?

In France this led to a law being passed in 1898 to protect hatters, however in the United States mercury was used in hat making until 1941, despite the fact that in 1888 a new method using hydrochloride was patented.

Why did milliners use mercury?

To make top hats and other hats from animal skins they transformed into felt, milliners had to separate the animal skin from its fur and then mat the fur together. This process — called “carroting,” because it involved mercury nitrate, an orange mixture of mercury and nitric acid — meant boiling and drying the fur.