Slip

What it is

Slip is clay plus water plus patience. At its thinnest it is a lubricant you squeeze onto the wheel head; at its thickest it is a structural adhesive that welds a handle to a mug; mixed to a precise specific gravity it becomes the casting body for slip moulds.

The most common studio use is joining. Scoring both surfaces, painting on slip and pressing them together creates a bond that is stronger than the surrounding clay, because the slip contains fine particles that interlock across the seam. A 50/50 blend of slip and the body being joined, sometimes with a pinch of sodium silicate for flow, is the standard recipe.

Slip also decorates. Coloured slips — engobes — can be trailed from a bulb, painted, poured or dipped over leather-hard work to build pattern before the glaze goes on. Because engobe and body shrink together, it moves with the pot rather than flaking off, provided the two are matched in shrinkage.

How to use it well

• Always score both surfaces before joining — slip on smooth clay slides rather than bonds.
• Match slip to the body it is joining, or shrinkage differences will crack the seam in the kiln.
• Keep a labelled jar of each body you use; a generic slip bin becomes unusable once bodies are mixed.
• Stir with a whisk, not a stick, to break up settled lumps before applying.

Safety notes

• Liquid slip dries into airborne silica dust when it splatters onto a bench — clean up wet.
• Adding raw oxide colourants to slip means handling metal oxides; wear a mask and gloves.
• Never pour slip down a drain.

Compatible materials

Clay bodies

• Made from the same body being joined or cast

Glazes & surface

• Compatible with all — slip sits under glaze

Where it sits in the process

Preparing and homogenising clay before forming.

Wedging  Clay & Preparation  Entry tier

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