I make a lot of small things that are a hassle to load and unload individually in a kiln. So a simple solution to being more efficient with my time and kiln space was to make bisque test trays. These are perfect for all my test tiles, small sprigged work, slip-cast work, and other odds and ends. It’s much easier, faster, and safer to load 20 to 30 items into 4 or 5 trays, which are then simple to load and unload in a kiln, rather than loading and unloading those same items individually.
I first started making these when I wanted to maximize the firing space in my test kiln. I made bisque trays that I could stack inside my test kiln and utilize all the space. Since they’re stackable, it also took away the need for kiln furniture. This helps reduce the wear and tear on my good test-kiln shelves. Another advantage of using bisque test trays, is not having to worry if a glaze runs off a stilted piece or an experimental test tile. If it does, it’s cheaper to make new test trays than to buy new kiln shelves. The trays can be made for any type of kiln, just use the appropriate clay body for your firing temperature.
Tray Size and Shape
I choose tray sizes that maximize how I use the space in my test kiln and regular kiln. Proportionally, they fit on my kiln shelves well and work with the heights of my kiln posts. The trays can be any shape and you can have fun with the profiles if you like. I have square ones, because my test kiln is square. But, I also have rectangular ones, to better fit on the shelves for my regular kiln.
I keep my chosen sizes and shapes uniform, though, so I can stack them if needed. Making them stackable is efficient when loading the kiln and also for storage when not in use.
1 Construct the trays by rolling out slabs by hand so the clay is compressed and dense.
2 Cut all the parts to make the tray, wait until they’re leather hard, then score and slip all connecting edges before attaching.
3 Use a loop tool to carve grooves in the bottoms of trays larger than 4 inches square to reduce cracking due to heat retention.
4 Add feet to the bottoms of trays larger than 10 inches square. Place the feet about 1 inch apart.
General Slab Dimensions
Construct the trays using ¼–3⁄8-inch-thick slabs, rolled out by hand so the clay is compressed and dense (1). This helps reduce potential cracking of the bottoms. The height of the walls varies between 1–3 inches tall. The taller walls are for trays that hold stilted work or for slip-cast parts and sprigged pieces. Any height is fine, but if they get taller than 6 inches, they don’t stack as securely, and the walls have the potential to warp.
Cut all the parts to make the tray (a bottom and 4 sides) and wait until they’re leather hard to fabricate it. Score and slip all connecting edges before attaching them (2).
Addressing the Tray Bottom
Depending on the tray size, you may need to carve grooves or attach feet to the bottoms. Flat surfaces in full contact with the kiln shelf hold more heat than the surrounding shelf area and this can cause cracks in the tray bottoms during the firing process.
If your tray is smaller than 4-square inches (an area of 16 inches), it’s typically not a big problem and nothing has to be done. Trays between 5–10 inches square (an area of 25–100 inches) should have grooves carved across the bottom using a loop tool (3). The grooves should look similar to what you see on a commercial tile. They can be spaced an inch apart and should be shallow. Trays larger than 10 inches square should have rails or some kind of feet added to the bottom to elevate it off the shelf (4, 5). You can use the ¼-inch-thick slabs you already rolled out to do this.
5 Flat surfaces in contact with the kiln shelf hold more heat than the surrounding shelf area. Added feet distribute the heat.
6 Stack trays with wax paper between them, then sandwich the stacked trays between drywall so they don’t warp when drying.
7 Bisque test trays make loading multiple small items or items requiring stilts much easier.
8 Firing test tiles in bisque test trays protects your kiln shelves from runny or splattering glazes.
You can be as fancy or as simple as you like when making the trays. Just treat them like shallow boxes and use a clay body that can withstand the highest temperature that you fire to. Stack the trays with wax paper as separators, then sandwich the stacked trays between drywall so they don’t warp when drying (6).
I really enjoy having these trays in the studio. They take the hassle out of loading small pieces and allow you to be very experimental with your test tiles (7, 8). Once your trays are made, I’m sure you’ll find many great uses for them as well.
Paul Andrew Wandless is an artist, author, educator, and curator currently living and maintaining a studio in Chicago, Illinois. Wandless is on Board of Trustees for Penland School of Craft. He has authored the books, Image Transfer On Clay, 500 Prints on Clay and co-authored Alternative Kilns and Firing Techniques. He’s also featured in Fundamentals of Screen Printing On Clay with Paul Andrew Wandless, available at the Ceramic Arts Daily Shop, https://ceramicartsnetwork.org/bookstore. To see more of his work, visit www.studio3artcompany.com.