Liner Glazing a Stoneware Mug

I will show you how to glaze a mug with a liner glaze inside and a colored one outside so that they meet in a perfect line at the rim.

B. Glazes

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There are decorative and functional reasons to glazing the outside and inside of mugs as a separate operation. First, liner glazes are far less likely to leach harmful things into food or drink. Liner glazed mugs advertise to your customers that you are thinking about this. There are aesthetic reasons to have a different glaze inside and out. If your mugs have thin walls, glazing them in one operation is much more likely to water log them (glazes are much less likely to crack or bubble when they dry quickly). This method enables handling the mugs seconds after the final outside coat so that you can sponge the foot ring quickly.

For this to work well your wax needs to be the right consistency (not too thick). And it needs to dry for a while to resist better. I have found the Laguna Premium Wax resist works well. But Reed Wax is even better. Also, your glaze must not be too thick or heavy. Adjust the slurry to 1.43-1.45 specific gravity and add epsom salts to gel it to creamy consistency (stir the bucket, pull out the spatula, it should stop in 2-4 seconds). That will resist well.

Links

Glossary	Liner Glaze Liner-glazing is a way to assure that your ware has a durable and leach resistant surface. It also signals to customers that you care about this.
Articles	Is Your Fired Ware Safe? Glazed ware can be a safety hazard to end users because it may leach metals into food and drink, it could harbor bacteria and it could flake of in knife-edged pieces.

Commercial glazes on decorative surfaces, your own on food surfaces

These cone 6 porcelain mugs are hybrid. Three coats of a commercial glaze painted on the outside (Amaco PC-30) and my own liner glaze, G2926B, poured in and out on the inside. When commercial glazes (made by one company) fit a stoneware or porcelain (made by another company) it is by accident, neither company designed for the other! For inside food surfaces make or mix a liner glaze already proven to fit your clay body, one that sanity-checks well (as a dipping glaze or a brushing glaze). In your own recipes you can use quality materials that you know deliver no toxic compounds to the glass and that are proportioned to deliver a balanced chemistry. Read and watch our liner glazing step-by-step and liner glazing video for details on how to make glazes meet at the rim like this.

By Tony Hansen
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