Especially in the 19th century, inorganic mercury in the form of mercuric nitrate was commonly used in the production of felt for hats.[14] During a process called carroting, in which furs from small animals such as rabbits, hares or beavers were separated from their skins and matted together, an orange-colored solution containing mercuric nitrate was used as a smoothing agent. The resulting felt was then repeatedly shaped into large cones, shrunk in boiling water and dried.[2] In treated felts, a slow reaction released volatile free mercury.[15] Hatters (or milliners) who came into contact with vapours from the impregnated felt often worked in confined areas.[10]