As with most glazes we use silica to form the almost glasslike vitreous surfaces that protect our functional stoneware pottery and make it food and beverage safe. Silica alone however, would not melt appropriately and needs to be combined with mixtures of metal oxides to act as fluxes and colorants, and, though after what I just told you it may seem odd, some of the glazes we create also need alumina to help stiffen them (to keep them exactly where we want them on the pottery). There’s a great deal of chemistry and experimenting involved in coming up with glazes that work well. You’re seeing just some of the small containers on the top shelves behind Vic. These are used for preparing smaller tests.
We want to ensure customer safety from elements that might leach into beverages and food. A true understanding of glaze chemistry, and particularly how the various elements combine and interact is needed. It’s not just lead that could cause health issues. Some potters resort to commercially prepared glazes. Others find a few glazes and spend years treating all of their work the same way. But at JoVic Pottery, part of our delight in working with ceramic materials comes from the creative process, the frequent testing and development of new surfaces, textures and colours. We develop all our own glazes as well as using engobes and slips to create unique finishes.
Some of our work receives multiple firings, and though the pieces may have gone through both a bisque and a mid-range stoneware firing, we’re not always satisfied to leave it at that. On some of the work the final glaze application requires a low-temperature firing in order to create a glaze that feels like velvet to touch. Other pieces may receive multiple firings at cone 6 oxidation. We develop glazes for art pieces, raku pottery and stoneware.
Sometimes we start with an engobe fired on during the initial bisque stage. Pottery is not matured (turned into stoneware) during that initial firing; rather it remains porous enough for us to apply glaze in liquid form prior to final firings. In the case of the platter detail shown here, the engobed and carved apron of the platter was waxed over before applying glazes. On this piece there are multiple layers of glaze applied at varying thicknesses to create depth and colour.
All of our functional stoneware pottery is free of lead or other minerals and oxides that run the risk of leaching into food, and it can be safely placed in your dishwasher too. There are, however, some truly decorative glazes used on our artworks. They can contain high amounts of manganese, lithium or cobalt. But don’t worry, we’ll never risk your health, and we minimize ours by wearing masks when we concoct these gorgeous finishes that we know will never come into contact with anything that will leach out of them in contact with foods and liquids.
Visitors to our studio are often surprised by the number of containers with glaze ingredients sitting on our shelves. We always welcome their questions, but we don’t share our recipes. The countless hours we invest in glaze development will ensure we keep these secret.