Bell founding first began with monks and other ecclesiasts casting their own bells from alloy of 14 parts copper and 4 parts tin. Other additions were gold ornaments and trinkets donated by generous parishioners; they probably thought it would bring them luck.
In due course, bell founding became a profession with itinerant bell founders casting bells in churchyards or nearby fields, until eventually the introduction of bell foundries.
It is thought that there are now only two bell foundries in England, Taylors and Whitechapel.
A Brief Guide to Campanology