Earthenware and porcelain are both ceramic materials that are made by mixing various types of clay with water, and then shaping and firing the objects. However, earthenware and porcelain are not the same. They are distinguished by the composition of the raw materials.
In the case of porcelain, finer raw materials such as porcelain clay (kaolin) and feldspar predominate. Earthenware is made from coarser types of clay. The composition of the raw materials determines the firing temperature of the ceramic. Porcelain has a higher firing temperature than earthenware. This causes porcelain to become hard, non-porous and even slightly translucent. Earthenware, on the other hand, is less hard, porous and opaque. Glazing prevents earthenware pottery to absorb liquid. On porcelain the glaze has a decorative function only.
Both Sphinx and Société Céramique produced mainly earthenware.