Glaze Chunks

Vase with colored glaze and porcelain top, 3 ft. 8 in. (1.1 m) in height, wheel-thrown porcelain, fired to cone 9 in oxidation, cast and sculpted glaze, fired to cone 02 in oxidation, 2019.

Honestly, I have never really enjoyed glazing. Don’t get me wrong, I truly appreciate those who flourish in this arena and the work they make, but for me, this part of the process has always been my least favorite. Glaze day was always a rush to get through as I was eager to get back to shaping things out of plastic clay. Those of you that relish time in the glaze room are probably enraged, but before you tear this page out of the magazine, let me just say, I really do love glaze as a material.

My interests lie within the transmutation of ceramic materials through time and temperature. This phenomenon is a major motivator for my work. Glaze becomes a sculptural material to play with, stack, and arrange like building blocks to create compelling compositions. Through the use of molds and varying firing temperatures, I cast liquid glaze into solidified chunks and employ cold-working techniques to alter them. It was this interest in the formulation of glaze as three-dimensional form that has led to the creation of the glaze chunk.

Inspiration and Research

Within the last few years, I have been very alchemically liberal and materially adventurous, working across many media and experimenting with a number of different processes and techniques. An attraction to the glass studio sparked my interest in learning and implementing traditional glass-casting and cold-working techniques. I have always been intrigued with glass artists’ ability to manipulate material at a molten state; the dramatic and theatrical qualities involved in sculpting hot, liquid glass are fascinating. I began searching for ways to echo these processes within my own practice.

Cup with blue saucer and green glaze chunk, 6 in. (15 cm) in height, wheel-thrown porcelain, fired to cone 9 in oxidation, cast and sculpted glaze, fired to cone 02, 3, and 1 in oxidation, 2019.

Soft-Brick Molds and Glaze Casting

My molds consist of soft bricks, kiln wash, wax resist, and steel wire. Originally, I chose soft brick for the molds because they are lightweight and easy to shape, but throughout the evolution of this process, the insulative properties of the brick have proven very useful in melting and cooling glaze.

To begin building molds, cut 5 rectangular pieces of soft brick: 4 pieces measuring 4½×1½×2½ inches for the walls of the mold and 1 measuring 4½×½×2½ inches for the floor of the mold. I have found these measurements safe and effective for casting about 800 grams of liquid glaze. A larger mold will increase the chances of the mold failing due to the amount of glaze that needs to be cast. The thickness of the mold pieces is crucial. Anywhere from 1½ to 2 inches for the walls and ½ to 1 inch for the floor will ensure a sturdy and stable mold. If the pieces are too thin, they will break when fastening the mold together with wire.

1 Apply kiln wash to the soft-brick mold pieces.

2 Apply wax resist over the kiln wash after it dries.

3 Assemble the soft-brick mold.

4 Bind the soft-brick mold sections together with steel wire.

Arrange the soft-brick pieces flat on the table and brush a thin coat of kiln wash onto the face of each brick (1). The kiln wash operates as a release that aids in the removal of the glaze from the mold after firing. Once the kiln wash has dried, apply a thin layer of wax resist to the face of each brick (2). The wax functions as a barrier, preventing the freshly cast liquid glaze from absorbing into the porous soft brick. Begin arranging the soft brick into a rectangular box (3). Cut two lengths of 18-gauge steel utility tie wire and wrap one piece around the lower half of the mold and the other around the top, making sure to twist out any bit of slack with pliers (4). Be careful not to over tighten and snap the wire or crack the soft brick. Once your mold has been washed, waxed, and secured, mix your glaze to the consistency of heavy whipping cream and pour it directly into the mold (5). The open-faced mold design (6) allows the glaze to dry rather quickly and makes it easy to move and load into the kiln.

5 Pour liquid glaze into the mold.

6 Once filled, the mold is allowed to sit until the glaze dries.

Firing

Beginning with recipes recommended for firing to cone 04, most of my firings take place between cone 05 and cone 02. Glaze that has been cast into molds requires a higher firing temperature to ensure the materials flux fully. Because the molds are made of soft brick, which naturally insulates, it is necessary to exceed the glaze’s maturing temperature of cone 04, by firing to cone 02. When glaze is applied free from the mold and directly onto an object in the form of a fired chunk, a lower firing temperature is necessary, but this also varies based upon the characteristics that are desired. For example, if I intend for a fired glaze chunk to maintain its faceted geometry while fusing it to a clay form, I would fire to cone 06½ (1830°F (999°C)). I often use a small amount of glaze as an indicator of the melt, much like a cone pack. This is a simple method consisting of a small piece of fired glaze on a slab of soft brick placed where it can be viewed through a peep hole in the kiln. I can see when the glaze starts to puff up, deform, or melt altogether, allowing me to shut off the kiln or fire it longer if necessary. If a drip or run on the glaze chunk is favored, I fire to cone 05½ (1900°F (1038°C)), again observing a bit of glaze through the spy port. A range of firing temperatures offers a wide variety of results, which lend themselves to different aesthetic considerations. All of the glaze-filled, soft-brick molds are fired on top of a layer of silica sand. The sand prevents any glaze that has leaked from sticking to the kiln shelf. A slow glaze firing schedule will suffice, but some testing might be required to achieve what is desired. It is important to wait until the kiln is below 150°F (66°C) before opening. This will ensure that the glaze blocks don’t cool too quickly, which can cause them to crack.

7 After firing, remove the tie wire from the soft-brick mold.

8 The fired glaze chunk with three sides of the soft-brick mold removed.

9 Use a wet tile saw to cut the fired glaze into chunks.

10 View of clean face of glaze block after trimming away the exterior using the tile saw.

Post-Firing Refinement

Once the chunks have been cast and fired, I spend time refining and altering their surfaces or shapes through cold-working processes that do not require the use of heat.

Begin by removing the solid glaze from the soft-brick mold (7, 8). Use a wet saw to detach any bits of soft brick that have fused to the sides or bottom of the glaze. Keep the glaze wet by turning up the water on the saw, to ensure that the blade doesn’t get too hot and crack or damage the chunk. Guide the blade gently through the glaze chunk, giving it plenty of time to cut the material (9, 10). If you move too quickly, you could ruin your saw blade. Note: Chunks fired to different temperatures will cut differently due to their densities, so it is necessary to adjust your cutting speed accordingly.

Using a 60-grit diamond sanding pad, begin gently shaping each glaze chunk by moving it back and forth across the pad (11). Check often to assess the amount of material being removed. Once again, continuously apply water while sanding to avoid heating and cracking the object or damaging the grinding pad. Repeat these steps with 120- and 240-grit grinding pads, depending on the desired surface texture.

11 Polish the glaze blocks using a grinding pad attached to a potters wheel.

Cup with pink glaze chunk and yellow handle, 3½ in. (9 cm) in height, wheel-thrown porcelain, fired to cone 9 in oxidation, cast and sculpted glaze, fired to cone 02 and cone 1 in oxidation, 2018.

Arrangement and Play

In the studio, I arrange multiple configurations and iterations of sculptural parts on my table at once. The parts come together in a ceramic vessel through a slow process, thinking through the importance of each element. A wheel-thrown cylinder becomes a mug as I fuse (in the kiln) or epoxy a cast chunk of brightly colored glaze to its side. Disparate parts converge into a familiar form, juxtaposing formal and conceptual, like color and glaze calculation.

The relationship between glaze and clay has evolved and transformed in many ways throughout the history of ceramics. The melting of glaze and the vitreousness of clay, for me, have become symbols of heat and melt. Within my work, the glaze chunk further investigates my interest in exploring the potential of the transmutation of ceramic materials through time and temperature. Naked clay forms adorned with solid chunks of faceted glaze curiously reference the amount of material necessary to cover an entire vessel and promote a reinterpretation of a traditional glazed surface. Glaze layers, surfaces, or skins are upended, squished, cut, or compacted; the product of these decisions manifests within a glob, drip, or a wonderfully tactile chunk.

Cup with yellow glaze saucer, 6 in. (15 cm) in height, wheel-thrown porcelain, fired to cone 9 in oxidation, cast and sculpted glaze, fired to cone 03 in oxidation, 2018.

the author Alex Zablocki received his BFA in ceramics from Finlandia University in 2008, pursued two post-baccalaureate programs at the University of Nebraska-Lincoln and Colorado State University, and completed a residency at Anderson Ranch Art Center. In 2017, he received his MFA from the New York State College of Ceramics at Alfred University. Alex is currently the visiting assistant professor of ceramics and sculpture at Alma College in Alma, Michigan. Learn more about his work at www.alexmzablocki.com.

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