Liner Glazing

Step-by-step to apply inside and outside glazes to a pottery mug and get them to meet at a clean line at the rim.

Details

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This page describes the technique of glazing pottery to make an inside and outside glaze meet in a clean line at the rim. The technique is common in commercial ware and requires precision to execute well. It is not only aesthetic but also functional - more durable and food safe glazes are appropriate on food surfaces. Separate glazing operations for inside and outside surfaces are also a practical production technique (e.g. for thin-walled pieces that would waterlog on a complete dip, where separate people or teams cooperate in glazing each piece).

Use glazes that do not have too much melt fluidity (run too much during firing), or they may bleed into each other across the join.
Use a thixotropic dipping glaze, don't put up with problems of excessive dripping, settling in the bucket and slow drying.
Form the mug (on the wheel) such that the lip flares out a little, this will reduce dripping down the outside on the outpour. Also, round the lip so the glaze join line occurs on a rounded contour.

Step-by-Step

Fill the bisque mug with liner glaze. Pour it out in a circular motion and then dip the lip. Hold it there long enough to get the thickness needed:
After the glaze has dried sufficiently, use a banding wheel to wax up the inside (starting about an inch down) and just up around the top of the lip.

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Using a sharp knife (e.g. Olfa cutter) in one hand and rotating the mug with the other, cut away the glaze (down to the bisque) up to the highest point on the lip (the best cut with the least dust is done when the glaze is still damp). Clean up any remaining glaze around the outside of the rim using a fettling knife. Now the inside glaze terminates at a perfect wax-covered edge at the lip.
Using a damp sponge, clean any remaining glaze off the outside up to the wax line. This is not always necessary, but note that the poorest surface to receive the outer glaze is one that is dry and has residue from not being cleaned off completely (pinholes and crawls occur). The second poorest surface is one that has residue but is still too wet from the inside pour (often true if the piece is thin walled). The best surface is one that is slightly damp and clean.
Glaze the outside. Keep your hands damp so they will not stick to the wax (and pull off sections as you touch it). Push the lip of the mug into the glaze 5-10mm (being careful to hold the mug level as you do this). Shake off the drips and immediately turn it over, put your hand inside, clamp against the inner surface and push it into the glaze right down to the rim (to overlap the lip dip just made). It may be tricky at first to push the mug down far enough and avoid glaze spilling inside.
Set the mug on a turntable to sponge away any drips left over the wax-covered areas on the inside top of the lip.
Clean the foot and set it out to dry.

Related Information

Liner Glazing a porcelain mug

The process of applying a liner glaze to the inside of a piece (by pouring), applying wax emulsion up the top inside and over the rim (using a turntable and brush), removing the glaze up the outside to mid-rim and finally dipping the rim and outside into the other glaze.