Process for the manufacturing of colored clay products

A process for the production of coloured, fired, shaped clay products which comprises firing shaped, dried, iron-containing clay objects in a kiln, depositing carbon on and into the resulting fired clay objects by heat treating the said fired objects in a carbon-containing atmosphere to product a coloured, fired, shaped clay product and thereafter cooling said coloured product in an atmosphere of nitrogen to prevent the loss or reduction of the colour produced by the carbon deposition step, said nitrogen atmosphere containing a small amount of oxygen in quantities and for times to cause a speckled effect in the final coloured product.

A process for the production of coloured, fired, shaped clay products which comprises firing shaped, dried, iron-containing clay obbjects in a kiln, depositing carbon on and into the resultant fired clay objects by exposing the said fired clay objects to the action of a carbon-containing atmosphere at an elevated temperature for a period of from 2 through 12 hours to produce coloured, fired, shaped clay products and thereafter cooling the resulting coloured, fired, shaped clay products in an atmosphere of nitrogen to prevent the loss or reduction of the colour produced by the carbon deposition step, and recirculating the nitrogen via a heat exchanger during the cooling period.