Topic: Ceramic Kilns

Tips and Tools: Firing on the Rim

Unconventional methods of stacking and loading kilns aren’t just a space, time, and cost-effective strategy in a studio practice; loading plates and platters on their rims can also be used as an effective tool for preventing drying and tension cracks.

Over the last 26 years, I’ve successfully bisque fired plates and platters of many sizes and weights on their rims. The technique of stacking wheel-thrown dinner plates on their rims in a vertical formation in a bisque kiln was first introduced to me by the 5th generation Japanese potter, Noboru Kubo. However, it was after several unsuccessful attempts to fire a 24-inch diameter, 25-pound platter in a traditional, horizontal configuration that made me significantly rethink my bisque kiln stacking practices.

The most common problem encountered when bisque firing a large platter is tension cracks or the dreaded complete blow ups. During a bisque firing, water is driven out of the clay and the organic residue burns out. Stacking plates and platters on their rims in a horizontal configuration allows for better air flow around the wares for the water to be driven off, and prevents water from being trapped under the bottom, preventing the blow outs. Additionally, on larger platters that would traditionally be fired in a horizontal configuration in an electric kiln, the vertical configuration alleviates temperature strain that sometimes occurs between the center and the outside wall of the kiln, which compounds the stress on the platters and can cause cracks.

1 When loading work vertically in a bisque kiln, begin with the sturdiest plate or platter and place it in the kiln with the rim touching the kiln shelf. Make sure that the bottom of the foot rests against the wall in front of the elements but does not touch the elements.

2 Brenda Danbrook’s fully loaded bisque kiln with vertically stacked plates.

 

Basic Principles for Loading the Wares

Optimally a sturdy rim that is at least ¼-inch thick is suggested. To date, I have used a wide range of Laguna and Plainsman clays from stoneware to porcelain. Jodi Dawson from Australia uses Walkers porcelain with success and no warping.

To begin, much like traditional loading of wares in a top-loading electric kiln, it is suggested to not load heavy forms on lighter ones. The principle is to try to achieve a near vertical orientation. Start by testing one plate or platter to ensure your clay body is suitable. Do not load in this way if any of the elements in your electric kiln are exposed and can come in contact with the wares. A soft brick can be placed in the kiln and used to lean wares on as well, instead of leaning them on the kiln wall.

To begin, place four 10-inch stilts in the bottom of the kiln in a square composition. Next, set the sturdiest plate or platter into the kiln in a vertical composition, being careful to not set the form down too hard and chip the rim. The bottom or foot of the plate rests against wall in front of the elements, but does not touch any of the elements. Following this step, a succession of similar size forms are leaned up against each other (1) and stacked one in front of each other until the desired depth is reached or the kiln is full (2). Generally, stacking no more than 6 plates on any given point on the kiln wall is suggested until the technique is fully tested. It is optimal to place single plates around the wall of the kiln individually when space allows rather than as a multiple stack, followed by placing bowls and cups in a traditional horizontal composition in the center of the kiln. Once the bottom of the kiln is filled, place the next shelf. When loading the top of the kiln, place forms singularly, working around the wall of the kiln to ensure the weight distribution is kept even and the shelf is not pushed off the kiln posts.

Loading a bisque kiln using this technique can be a great tool when trying to save space or to eliminate the stress cracks that can occur when firing large platter forms. Happy firing!

3 Brenda Danbrook’s lunch plate, dinner plate, and serving platter, to 14 in. (36 cm) in length, stoneware, slip, fired to cone 10 in reduction, 2017. All three vessels were bisque fired vertically.

the author Brenda Jane Danbrook is from Opal, Alberta, Canada, but currently is a MFA candidate at the University of Regina, Saskatchewan, Canada. To learn more, visit www.bdanbrook.com or Instagram: Bdanbrook_ceramics.

Send your tip and tool ideas, along with plenty of images, to editorial@ceramicsmonthly.org. If we use your idea, you’ll receive a complimentary one-year subscription to CM!

 

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