Recently I paid a visit to April Grigsby’s (of April Grigsby Ceramics) pottery studio to learn about making bonsai pots and try my hand at making one of my own.
April has been working with clay since she was 6-years-old and majored in Ceramics at the Columbus College of Art & design. One of her pots even took second place at the 2nd National Juried Bonsai Pot Competition. She took a break from ceramics soon after that but eventually found her way back and now combines her lifetime of ceramics experience with her love of bonsai (she's a former president of a Florida bonsai club) to create beautiful and functional pots which are especially suited to bonsai hobbyists and professionals alike.
We started the tour at the end of the pot-making process as I got to see her newest appliance, a high-tech electric kiln.
This kiln is large enough for pots a little over 20 inches and the firing schedule is all digitally controlled. This level of control allows for precise timing of each stage of the firing (temperature and length) so that moisture can be slowly driven out of the clay before the intense heat hits, reducing the chance for breakage. This particular kiln has heating elements on the sides and bottom to keep the heat consistent within the appliance.
She also has an older propane kiln but that one is on wheels and has to be wheeled outside for proper ventilation, which requires a close eye on the weather to avoid rain or snow!
April is able to use "furniture" to build custom-sized shelves within the kiln so it can be efficiently packed full of pots. A given firing can be in excess of 16 hours so it is important to get the most use out of every inch of space. Firing is often done in two stages, with the first firing (bisque firing) turning the clay into ceramic. If the pot is to be glazed, it is then cooled down, the glaze is applied, and the pot undergoes a second firing to melt the glaze onto the pot.
While the digital controls are very accurate, April still prefers to verify with pyrometric cones, aka "witness cones," which are designed to melt at a specific temperature so that when the firing is done she has an indication that the proper temperature and length of time was reached. They also serve as an early warning if the temperature settings need to be adjusted for future firings.
One thing that is important for bonsai pots in particular is that they are vitrified
, or heated to a state where the clay is nearly converted to glass so that there is very little moisture remaining in the finished product. Any superfluous moisture could crack under freezing conditions. In addition, April uses clay that has very low porosity so that water isn't absorbed back into the finished pot which could later freeze and crack. Finally, she is careful in her designs so that most of her pots do not have an inward-turned lip. As the root ball of a bonsai freezes it expands and lifts up in the pot. A pot with an inward-turned lip can prevent the root ball from rising and crack the pot.
The tour continued into the studio where April showed me her two potters wheels used for "throwing clay". In the picture on the right, the nearest wheel is her newer one while the smaller one closer to the wall she has had for decades. She frequently uses the smaller more familiar one for trimming and finishing a pot. An added benefit is that she's able to save time by not needing to clean out the "splash pan" every time she starts to throw since the trimming process doesn't require the wheel to be spinning at a high rate. The scraps also have more time to dry. This makes recycling easier because dry clay "slakes" (disintigrates) down more quickly when added to water.
Because it is spinning, pots made on the wheels are round, or nearly round. However, after being thrown the pot can be re-worked to oval, square, rounded-square, or other shapes. This necessitates that the bottom of the pot be cut off so that the sides of the pot can be re-shaped, since the bottom of the pot cannot change shape. More on that in a minute.
If she's building a pot with clay slabs, she will use her rolling table to flatten the clay, which typically comes in 25lb blocks. Once the clay is flatted the slabs can be used to build a pot, become a pot bottom, or can be pressed and shaped over a mold to make intricate pot shapes. For pot bottoms, the bottomless pot is placed on an appropriately sized slab and the inside of the pot is traced into the slab. Marks are made on the slab and the pot to line it up and then the slap is cut, scored, and pressed into place. Slabs for pot bottoms are rolled out immediately after the pot is formed so that the clay for both parts dry at the same rate. If their moisture content isn't similar then assembly may be impossible.
Pots can also be made by rolling clay into a coil and slowly building up the shape of the pot, or by making a "pinch-pot" where a ball of clay is worked by hand into shape.
April has a myriad of tools, molds, pattern stamps, etc. While she does occasionally buy commercial glazes she prefers to make her own and has a shelf full of the powdered ingredients she mixes according to precise recipes. For the pots that are getting a glaze, she can dip, paint it on, or use her custom spray booth.
A pinch-pot is what I made as part of my visit. You can see the pictures of the finished product below. Not perfect, for sure, but not too shabby for my first bonsai pot! Though, I did have in mind this pot being for a kusomono (grass & flower planting).
I started with a small ball of clay and slowly pinched the center of it down and away to make the bowl shape. This was refined by setting it on a small non-powered turn-table to allow for more easily shaping and smoothing the clay with my fingers, scraping tools, and sponges. The thickness of the walls and bottom can be tested with a small needle tool inserted into the clay. When I had the desired size and shape, April helped me to level the sides and punch drain holes. I opted for two fairly large drain holes and since it was for a kusomono planting I did not add wire holes to the pot. After that, April showed me how to make rolls of clay into feet and attach them to the pot by scoring the clay and applying water before pressing firmly into place. Finally, I signed and dated the pot. It will take several days to dry and will then be fired. I decided not to glaze this pot so it will be the natural color of the clay.
Overall it was a fun and educational trip. April is a master of her craft and her pots are in high demand (as of this writing, Black River Bonsai is completely sold out!) and I enjoyed seeing the process of making pots. I also came away with a greater appreciation for the amount of work that goes into making every pot.