In the metallurgy of copper blister copper is obtained from

• Blister copper is a form of impure copper that is obtained in the self-reduction process during bessemerization. 

The following reaction takes place in a furnace :

                                  $2{\mathrm{Cu}}_{2}O+{\mathrm{Cu}}_2\mathrm{S}⟶6\mathrm{Cu}+{\mathrm{SO}}_2$

The molten metal is cooled in sand molds SO₂ escapes. The resultant impure copper metal is known as "Blister copper".