- Cast iron, with a carbon percentage of 2.5 – 6 %.
- Steel, with a carbon percentage of 0.15 – 2.5 %.
- Soft iron, with a carbon percentage of less than 0.1 %.

The higher the percentage of carbon, the harder the metal is but also the more fragile it is, although later it may be possible to combine it with other metals that give it other characteristics. Nickel makes it harder, as does chrome, which also serves to prevent corrosion.

Cast iron: Must be polished with a Corundum compound and a sisal or sisal cloth buff (vas)

Steel: There are basically three types of stainless steel:

Martensitic Steels: Can be hardened. They are magnetic and easily machined. They have a chrome content of between 13 and 17 % and a nickel content of 0 to 2 %. When quenched they are more resistant to rust. Always treated with Corundum or alumina compounds and sisal or sisal cloth buffs.

Ferritic steels: These are not susceptible to quenching and are only slightly magnetic or not magnetic at all. They are basically composed of iron and chrome, and the latter can reach proportions of up to 27%. These are always polished with Corundum, alumina or silicon carbide compounds and sisal or sisal cloth buffs.

Austenitic Steels: These are chrome-nickel steels (18/10), they are not magnetic and are the most resistant to rust and corrosion. They are polished with alumina compounds and sisal or sisal cloth buffs.

Ferric metals may be treated in different ways:

- Heat treatment: Annealing, quenching and tempering.
- Thermochemical: Cementing, cyanide hardening, nitriding, carbon nitriding and sulphurization.
- Mechanical: In cold, deep shaping, superficial shaping, in hot and forge.
- Superficial: Hard chrome and metallization.