CALCIUM OXIDE

The melting point of calcium oxide is 2572 degC. This white, caustic crystalline substance is often called burnt lime or quicklime. It is manufactured by thermally decomposing materials like limestone, coral, sea shells or chalk, which are mainly calcium carbonate (CaCO3; mineral calcite), in lime kilns until the carbon dioxide is driven off. This process is known as calcination.

Calcium oxide is a Lewis base and can donate pairs of electrons to oxygen molecules. As such, it is a diamagnetic compound (it does not attract magnetism). It is also an odorless material.

In ceramics, calcium oxide is used as a flux in medium and high temperature glazes. It starts its fluxing action in a glaze around 1100C and increases its viscosity, surface tension & expansion/contraction rate. It also has a moderate effect on colour (e.g. it can make iron oxide appear bluish), except in low molar amounts where it will produce the characteristic ‘lime matte’ in fluid glazes.

The chemical can be handled under normal conditions, but it is hazardous by inhalation & skin contact. It can also cause acidosis if it is ingested. See the Safety Data Sheet for further details.