Five Reasons to Convert Cone 10 Reduction Glazes to Cone 6: A Potter Shares His Rationale and His Recipes
Today, Rick Malmgren explains the benefits of firing his reduction glazes lower and shares some of his great cone 6 reduction glaze recipes.
Though many are unaware of it, poor glaze fit can reduce the strength of a fired ceramic piece to as little as one-fifth the strength of a similar piece with ideal glaze fit. While good glaze fit seldom occurs by accident, it can be planned for and controlled. Some ceramic artists use glaze fit to induce crazing as a decorative technique (crackling) while others artists may want to avoid a “crackle” glaze.
In today’s post, we are presenting a little intro to glaze mixing and testing from Richard Zakin. In it he explains how the glaze making process is easily mastered if you have the right tools, follow an ordered procedure, and take the work seriously.
Phases are specific forms of materials. The most familiar phases are solid, liquid and vapor. Any phase of a material is identical in composition and structure in all parts of that phase. For instance, a glass of water is the liquid phase of H2O, top to bottom; if it weren’t, we’d call it something else, like ice if it were solid (structural change), or lemonade if it had lemon and sugar dissolved in it (compositional change).
Beautiful, soft, muted-color brushstrokes and washes of water-soluble metal salts decorate Gary Holt’s translucent porcelain bowls and plates. The simplicity and quiet presence of his works belie the years that Holt spent experimenting and perfecting his technique. Using water-soluble metals salts (WSMS) demands excellent technical skills and careful attention to details.
Barium carbonate has long been used as an ingredient in high-fire glazes, sometimes conferring unique properties upon glazes. One of the alkaline earth carbonates, it has also been used as rat poison (large doses can be toxic to humans as well). Glazes containing it ought to be checked for barium leaching if they are intended to hold food or drink, or reserved for surfaces that do not come into contact with food. It is not my intent to present the research on barium toxicity here, but to present a course of action for replacing it in glazes.
One of the more fascinating, sometimes frustrating parts of ceramics is learning to balance the innumerable factors that affect the outcome of a firing. Glaze ingredients, the clay body used, firing cycles, atmospheres, kiln-stacking techniques and geography (to name a few variables) can all affect firing results.
How many times have you copied a glaze formula, only to find that it didn’t work as expected? It is not unheard of for glazes with the same formula to produce different results. While this may seem like a dead end, it does not have to be.
It Slices, It Dices! Some Simple Glaze Tests Reveal a Ceramic Glaze That Can Do it All (well, almost)
Kristina Bogdanov, who teaches at Ohio Wesleyan College in Delaware, Ohio, was intrigued when she realized that one of the class glazes seemed to fire well at cone 10 reduction in a gas kiln, cone 6 in an electric kiln, and cone 9 reduction in a soda kiln without any change in the recipe. So she ran the glaze through a battery of tests to see just how versatile it was. Today, in an excerpt from the 2010 Buyers Guide for Ceramic Arts, Kristina explains her testing process and the results.
As John Britt points out in today’s post, firing to cone 6 reduction is cheaper, faster, and the results can be almost indistinguishable from high fire.