Paste

SOFT-PASTE PORCELAIN

Soft-paste porcelain, known as ‘pâte tendre’ in France, is artificial porcelain. It shares many of the features of ‘true’ or Oriental porcelain, transmitting light, a white body or paste, but it lacks the critical ingredient, kaolin or china clay, and can crack if exposed to boiling water. In France, artificial porcelain was commercially produced from the late seventeenth century at the Saint-Cloud manufactory, just outside Paris. It contained a glassy frit (calcined and ground to a powder), mixed with white clay and chalk.

Objects were fired before glazing, when there was some shrinkage, and fired again when covered with a lead-glaze, sometime made opaque and whiter with the addition of tin oxide. The term ‘soft’ refers to the lower temperatures required compared to hard-paste porcelain. Soft-paste was an expensive process owing to the many losses resulting in sagging, firing cracks and blemishes. It was produced at Sèvres until 1804, when it was discontinued when hard paste was produced exclusively.

BISCUIT

The term ‘biscuit’ describes porcelain, either soft-paste or hard-paste, which has been fired but not glazed. It refers either to unfinished pieces waiting to be glazed, or to completed unglazed figures and miniature vases on columns, often used for table decorations which were not intended to be glazed. The surface resembles sugar sculpture for the dessert table or statuary marble. The term, meaning ‘twice fired’, may refer to the initial firing of the frit, in the preparation of the clay and second firing once modelled.