I have a long history of using sculptural glazes with frowned upon or, more appropriately what I call “use with caution” materials, such as lithium carbonate and barium carbonate. These wonderful textural glazes give great depth and variety to sculptural forms, architectural pieces, and tiles. Many people finish sculptural and abstract work with cold finishes, but for a glaze fanatic like myself, these recipes are really fun to work with.
Crusty Beady Glazes
You can achieve a crusty or sugary look by altering a glaze with added silica (a glass former with a high melting point), added alumina (a refractory or a stiffening agent, helping glazes to stick to a pot’s vertical surface without running off while being fired), or by further changing a recipe’s melting point with a combination of the two.
You can also add magnesium carbonate and/or Cornwall Stone, which will cause a glaze to bead up and or crawl when they’re fired. Each will make a sort of crawl glaze on their own; however, by adding other materials, you can really make things interesting.
A note on color: Lithium carbonate often flashes or creates a pearl-like quality such as the pink in Glaze 1, or in other instances it can eat away at the stain as with Glazes 4, 5, and 6, while the dramatic green in Glaze 2 is a reaction between the turquoise stain and the recipe ingredients.
Barium carbonate, lithium carbonate, and fluxes that contain lithium can impart a pearlescent or sparkling quality to a glaze. Caution: These recipes are not suitable for surfaces that will come into contact with food—most have soft, heavily textured surfaces that would be impossible to clean and include high concentrations of ingredients like barium carbonate, which are not considered food safe.
Preferred Clay to Use
You may experience some shivering when using these glazes on low-fire clay bodies. When I was working sculpturally, I found that many of these glazes had a better success rate on high-fire clay bodies. I bisque fired to cone 02 or 2 to harden or vitrify the clay a bit more, then fired the glaze to cone 06 or 04 to achieve the surface I wanted.
Have fun with these recipes. On sculpture, there’s no right or wrong answer when playing with materials, and mixing recipes like these is a fun way to learn the limits you can push a glaze to before it runs off the piece, shivers, or looks amazing!
Note: All glazes were sieved with a 40-mesh sieve, brushed on Little Loafers and white earthenware with grog from Highwater Clay, and fired in an electric kiln on a medium cycle.
Deanna Ranlett has been working with clay and glazes for 18 years. She is the owner of MudFire Studio and Gallery in Decatur, Georgia. To learn more, visit www.mudfire.com.