How to Dramatically Expand Your Glaze Palette Through the Magic of Glaze Layering Erick Howenstine

When it comes to studio glazes, the possibilities go far beyond using a single glaze on a single surface. By layering glazes in different combinations and orders, ceramic artists can uncover unexpected colors, textures, and effects. 

Students at Northeastern Illinois University in Chicago typically fire at cone 10 in both gas and electric kilns, using a set of twelve tried-and-true glazes. They’re often surprised by unexpected effects when one glaze has overlapped another, maybe at the rim when different glazes were applied inside and out, or more dramatically when combinations were applied elsewhere by spraying, painting, or dashing on. Sometimes they’re pleased, sometimes disappointed. Occasionally, their piece is ruined and the shelves are damaged by thick or incompatible combinations running off. 

Surfaces are affected by the kiln atmosphere (gas/reduction or electric/oxidation), the thickness of a single glaze, and by the clay body. But, the effect can be even more striking and surprising by simply altering which of the two glazes is applied first. 

Creating the Display 

To show students what they might expect from any combination of two glazes, we’ve created two compact tile displays showing every combination, in either order, for gas and electric environments. Each display uses a single clay and one firing method. 

As the chart and images illustrate, our twelve base glazes appear alone on the bottom two rows of the display, thick or thin, left and right. The larger tiles are fixed to the board (to maintain order), and these also reveal the clay body (by way of wax resist before glazing). All other tiles are hung on nails for removal and closer inspection. Each has a stamped texture, which adds yet another dimension to the display, as glaze generally accumulates in notches and remains thin on ridges. 

In addition to their names, each glaze is numbered. The back of every removable tile indicates (by underglaze pencil prior to wax resist) which two glazes were used. The board behind the tile has the same information, so students return the chips to the right spot. 

Each double-glazed tile is dipped diagonally from corner to corner with one glaze, then fully with the other, followed by halfway again with the first glaze. This leaves one triangular side with glaze #1 over glaze #2, and the other side with #2 over #1. 

These smaller square tiles, 66 in number, are hung by corners, creating a triangle illustrating every combination. For a studio with five standard glazes, just fifteen tiles would be needed to show twenty-five effects, including each glaze alone, every combination, and every combination again in the opposite order. With our twelve glazes, there are 144 different results. 

Reading the Display 

The board is read this way: Start at the bottom with any two base glazes and follow them up diagonally until the rows intersect. That tile combines the two; on the left side of the tile, the left glaze is above, and on the right side of the tile, the base glaze from the right is on top. 

For example, in the illustration (a reduction atmosphere with a light brown clay) follow Old Gold (#4) up and to the right two steps until it intersects with the diagonal up and to the left from Copper Red (#6). Old Gold over Copper Red is an interesting tan—but if Gold is dipped first, the result is a dynamically speckled purple. 

This has been greatly appreciated by students trying to find the right effect for a piece, even if just deciding whether to glaze the inside before or after the outside is done. Especially given these new options, caution is essential. New students are often tempted to use a pleasing combination for the entire piece and dip the whole thing twice. Thick glazes alone may run; double dipping makes it even more likely. Students are advised to stop the second dip well before the bottom, and/ or create a notch or groove near the base of a thrown piece, which often stops the drip. 

Anyone using this double-dipped technique for a display may find it prudent to make a good number of extra tiles with the same clay. If a glaze is later replaced by another, the number of tiles needed to update the display is N-1, where N is the number of glazes in the studio. An additional glaze is easy to add, again with N-1 tiles, by adding another diagonal row to the right. If a glaze is retired, the display collapses nicely, although there will be a missing digit. This may suggest abbreviating the glaze name rather than using numbers. 

Finally, because results often vary with clay bodies, the kiln atmosphere, and nuances of glazing, it’s useful to make a note of the combinations used before firing. One can still learn more with every kiln load. 

the author Erick Howenstine, a potter and sculptor for 50 years and now retired, works in the ceramics studio at Northeastern Illinois University. He still enjoys teaching, making faces, and throwing things. To learn more, visit mugshotpottery.com.