Salt glazing is a fascinating ceramic technique, steeped in history yet vibrantly alive in contemporary practice. It’s a process where ordinary sodium chloride, common table salt, is introduced into a kiln at incredibly high temperatures, generally between 1200°C and 1300°C (2192°F to 2372°F). The vaporized salt then works its magic, reacting with the silica in the clay body to form a distinctive, often textured glaze. It’s a process that yields unique results, a testament to the alchemic dance between fire, salt, and clay.
One of the critical aspects of salt glazing is selecting the right clay body. Not just any clay will do; it needs to withstand the harsh conditions and high temperatures, and more importantly, it needs to play well with the salt. High silica content is key, as the sodium from the salt seeks out the silica to create that signature sodium-silicate glaze. A balanced alumina content is also important for the durability and stability of the glaze, with some suggesting an ideal silica to alumina ratio of 5:1 for optimal results. Thermal shock resistance is another must-have, and this is often achieved by incorporating materials like grog or sand into the clay. Common choices include fire clays, stoneware clays with added grog, and even certain porcelain clays that have been adapted for the process. For example, a clay like “Wood & Sagger WC419” is specifically designed to accentuate the effects of salt firings, while Windsor Porcelain can become beautifully translucent when thin and fired to cone 10.
It’s crucial to choose the correct clay. The clay must withstand high heat, and contain high silica content in order to interact correctly with the salt during the glazing process.
But how does the salt actually get into the kiln? There are several methods, each influencing the final glaze in its own way. One common technique involves introducing salt through designated ports in the kiln, sometimes packed in small paper sachets or using a long piece of angle iron to deposit the salt deep inside. Some potters use salt-soaked materials, like wood, to create unique glaze effects as the salt is gradually released during combustion. Spraying salt solutions into the kiln is another option, allowing for a more controlled application, while others soak textiles in brine and wrap them around their pieces for localized glaze effects. Artist Paul Soldner even described a method where salt is wrapped in newspaper to form a “salt burrito,” strategically placed in the flame path of the kiln. You can find more information about salt and soda glazing here, and here’s a guide on how to do salt glazing. There is also some information about salt glaze pottery on Wikipedia, and more information on Paul Soldner’s Website.
Of course, safety is paramount when working with salt glazing. The process releases sodium chloride vapors, which can be irritating to the respiratory system, and corrosive byproducts like hydrochloric acid (HCl). Proper ventilation is essential, and kilns should be equipped with efficient exhaust systems. Protective gear, including respirators with acid gas cartridges, acid-resistant gloves, and safety goggles, is a must. Regular kiln maintenance is also crucial to address any signs of corrosion caused by the acidic byproducts. Beyond safety, it’s also important to be aware of some potential defects that can arise in salt-glazed pottery, such as the “orange peel” texture or excessive pitting. Adjustments to glaze composition, firing schedules, and clay preparation can all help prevent these issues. More information on this can be found here. Salt glazing requires high firing temperatures, so it would be useful to check out this article on firing temperatures. Want to learn more about the process? Then check out unlocking the secrets of salt glazing.
Despite these challenges, many contemporary artists continue to explore and innovate within the realm of salt-glazed pottery, including Jane Hamlyn, known for her functional pottery and discovery of the green color achieved with a titanium wash, and Mark Hewitt, known for his large-scale wood-fired pots. Salt glazing is more than just a technique; it’s a journey of discovery, a blend of science and art that continues to inspire and challenge potters today.
