Slip-trailing

Slipware is pottery identified by its primary decorating process where slip is placed onto the leather-hard clay body surface before firing by dipping, painting or splashing. Slip is an aqueous suspension of a clay body, which is a mixture of clays and other minerals such as quartz, feldspar and mica. The slip placed onto a wet or leather-hard clay body surface by a variety of techniques including dipping, painting, piping or splashing.

Principal techniques include slip-painting, where the slip is treated like paint and used to create a design with brushes or other implements, and slip-trailing (or barbotine decoration), where the slip, usually rather thick, is dripped, piped or trailed onto the body, typically from some device like the piping bag used to decorate cakes.

Often only pottery where the slip creates patterns or images will be described as slipware, as opposed to the many types where a plain slip is applied to the whole body, for example most fine wares in Ancient Roman pottery, such as African red slip ware (note: "slip ware" not "slipware"). Decorative slips may be a different colour than the underlying clay body or offer other decorative qualities. Selectively applying layers of colored slips can create the effect of a painted ceramic, such as in the black-figure or red-figure pottery styles of Ancient Greek pottery. Slip decoration is an ancient technique in Chinese pottery also, used to cover whole vessels over 4,000 years ago.

A coating of white or coloured slip (sometimes called by the French term engobe in American English) can be applied to the whole body of the article, or just one part, such as outside or inside of a cup or jug, to improve its appearance, to give a smoother surface to a rough body, mask an inferior colour or for decorative effect. Slip can also be applied by painting techniques, in isolation or in several layers and colours. Sgraffito (or "sgraffiato") involves scratching through a layer of coloured slip to reveal a different colour or the base body underneath. Several layers of slip and/or sgraffito can be done while the pot is still in an unfired state. One colour of slip can be fired, before a second is applied, and prior to the scratching or incising decoration. This is particularly useful if the base body is not of the desired colour or texture.

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Wikipedia