The metal casting of the internal shape is made from metal, usually a lead alloy of about 40% lead with other elements added, which vary depending on the company and the item being made.
Once cast, this core is loaded into a press and a plastic formation made around it. The plastic cast, complette with its inner core is then submerged in a liquid which only effects the metal, such as lutron. Once the core has been removed the plastic moulding is passed through a wash ready for handeling by operators who perform any other required tasks to complette the manufactured item.