Technical terms used in the ceramic sector.

Clay: is the term that defines an extremely fine non-lithified sediment (the dimensions of the granules are less than 2 μm in diameter) consisting mainly of hydrated alumino-silicates belonging to the phyllosilicate class. Slip: clay made creamy by mixing it with water. Used as glue (binding) between pieces of clay. (e.g. cup and handle). Biscuit: this is the name given to any object made of clay, after having undergone the first firing. Depending on the type, clays fire on average at temperatures between 900 °C and 1050 °C. Semi-finished ceramic product: means a particular product that requires further processing to be marketed as a final product. In other words, the semi-finished product has no other function than its subsequent processing. Colombino: clay thread. Hence the technique. Craquelè: effect due to particular glazes, similar to a spider's web, occurs with the shattering of the covering of the object. Crystalline or Vetrina: colorless enamel, it has the particularity of allowing the grain and shade of the biscuit to shine through. Aspersion: action of enamelling, pouring the enamel itself onto the object. Raw: dry clay or glaze not yet fired. Leather hardness: drying state in which the clay is no longer mouldable but not yet ready for firing. At this stage, however, it is suitable for engraving and for gluing other pieces onto it. Stoneware: vitrifying mixture, made up of natural clays or multiple clays mixed together with raw materials such as silica and feldspar, is fired at a high temperature, between 1200 and 1300 °C and resistant to temperature variations. Engobbio: creamy clay of natural color or colored with metal oxides. It is applied to the surface of the object at leather hardness to change the color of the underlying clay. Warping: inconvenience caused by drying too quickly or in the case in which an object has been placed to dry near a heat source or in the middle of an air current. Knead: work the clay to make it uniform and without air bubbles. This operation is necessary if you want to recover clay waste. Lusters: metallic salts on fired enamel and third-fired at around 700 °C. Majolica: biscuit covered with tin-based enamel on which a design is made and fired a second time. Muffle: oven chamber made of refractory bricks, which protects objects from direct contact with fire. Foot: base or support of a ceramic object, very useful for facilitating cleaning of the object and preventing it from melting on the support surface in the oven during cooking. Plasticity: state in which the clay is mouldable. The degree of plasticity varies from dough to dough. Dusting: handkerchief filled with charcoal dust used in the dusting technique. Raku: oriental technique of making pottery with rapid firing. Refractory: melt-resistant ceramic material. Almost all the internal components of ovens and the equipment for baking objects are made of this material. Reduction: cooking in an oxygen-free atmosphere. Reserve: fatty substance that is spread on a part of the biscuit or a glaze to isolate it while proceeding with the decoration. Shrinkage: Shrinkage of clay during drying or firing. Each clay has a "personal" shrinkage percentage, it is the skill of the potter to control its proportions. Glaze: vitreous coating used to cover and decorate the ceramic object. Covering under paints: they are similar to engobes and can be applied both to the raw object and to the biscuit. They need crystalline to vitrify. Under transparent paints: they are applied as under covering paints, but unlike these they remain transparent. They are also used in the majolica technique. Dusting: perforated drawing on paper that is transferred onto the raw enamel by dabbing with a small bag full of charcoal dust or pulverized graphite. Stannifero: white, opaque, shiny glaze containing tin, used in the majolica technique. Terracotta: clay fired between 900-1000 °C. not crystalline or enamelled. Earthenware: clay with a white color widely used in casting techniques or if it is immersed in crystalline. Vitrify: make waterproof with the use of crystalline or enamel.