Iron is by mass the most common element on Earth, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust. Pure iron is relatively soft, but is unobtainable by smelting. The material is significantly hardened and strengthened by impurities, in particular carbon, from the smelting process. A certain proportion of carbon (between 0.002% and 2.1%) produces steel, which may be up to 1000 times harder than pure iron.
Resin is a "solid or highly viscous substance," which are typically convertible into polymers. Such viscous substances can be plant-derived or synthetic in origin. They are often mixtures of organic compounds. It is durable and transparent, and starts as a liquid form. After casting, it becomes solid and resilient. Special resin molds with smooth surfaces are created to give it a glossy finish.