I have always been drawn to atmospheric firing, whether salt, soda, or wood. However, I encountered a major drawback while using glazes to create imagery. The images I spent hours working on were either dissolved by the salt or soda fumes or obliterated by wood ash. Since the basis of my work is to use imagery to convey my concern for the natural world, I had to come up with a solution, namely a more durable material to illustrate with. Through trial and error I began to use slips while decorating. I found that slips responded favorably to atmospheric firings and could handle far more abuse. They lend texture, color, and stability to the illustrations allowing well-defined lines to remain intact with the build up of subsequent layers.
I think of slips as belonging to two camps, bisque and leather hard. As a general rule if a formula contains more than 50% clay, it’s intended for use on greenware, and if it contains less than 50% clay, it’s intended for bisqueware.
1 Wedge 7 pounds of clay and center it on a 12-inch bat. Open the base so it’s wide enough to be stable once it’s thrown taller.
2 Throw a cylinder to the desired height while maintaining a cone shape.
3 Shape the jar with a rib. Measure the rim opening and allow it to firm up.
4 Trim the exterior surface to reveal the groggy texture of the stoneware.
When decorating on leather-hard surfaces, I coat each pot with a white slip. The white base enables the flashing slip to produce the desired yellow, peach, and pumpkin hues you see on my crane plate (see page 20). Without the white slip, the surface would go muddy brown. Once leather hard, I sgraffito patterns or various animal imagery such as cranes, owls, and foxes into the slip by incising the surface with a sharp fettling knife. The knife achieves crisp, sweeping lines that will not budge during the firing. This incised border acts as both a guide and a barrier when waxing over the imagery in the bisque stage and applying flashing slip to the remainder of the pot. For best results, I use durable tools made of straw, bamboo, or wood (A).
Using a bisqueware slip can be a rewarding but risky venture. Formulation must be precise to fit the bisqueware. Too much shrinkage can cause it to pull off the pot while too little can cause shivering. Over the years I have learned a few tricks for success. Borax is a great additive. It acts as a cementing agent for the slip, allowing it to be glazed over. In order for this to happen the slip should dry on the pot for at least 24 hours. This eliminates peeling and flaking when applying glaze. I also enjoy using bisque slip over oxide washes to build up depth and layers. I use red iron oxide and black Mason stain washes along with wax resist for various designs such as barbed wire and dogwood. When dipped into the bisqueware slip, the pooling and dripping around the wax creates subtle variances in thickness’ that are hard to achieve through other techniques. The work can then be glazed once the slip has set.
5 Clean the bottom edge with a wooden knife, cut the jar off the bat, and bump in the bottom.
6 Center and open 1 1/2 pounds of clay for a lid. Open the mound, pull up the wall, and shape the lid with a rib. Check the width.
7 Allow the lid to firm up, then trim the top of lid to bring out the grog texture.
8 Wax the rim, then brush a red iron oxide wash on the jar and the lid exterior.
Mark Making for Specific Forms
All of my forms are simple and straightforward. The simplicity of the form allows me to use the surface as a blank canvas to place imagery on. I approach imagery through traditional Mingei ideals (the idea that common utilitarian goods can be inherently beautiful and available to all), and believe patterns and illustrations should be created with as few strokes of the brush as possible. This leads to a more accurate portrayal of the subject and gives each line more power in the composition.
Deciding what image to place upon a particular piece involves a certain amount of intuition. I look at the form and consider how a line, pattern, or more elaborate scene will interplay with it. Plates lend themselves to almost any decoration, but I’m mindful of the interaction it may have when food is placed upon it. Patterns work well on round forms such as low bowls, yunomi, and capped jars since the viewer only sees one portion at a time. Oval vases and large platters are well suited for more elaborate imagery such as landscapes.
Considering a Capped Jar
The idea for a capped lid form began after a night of baking. I found that the ceramic jars I had for flour and other various dry ingredients didn’t have large enough openings to fit measuring cups, because the inset lids decreased the size of the opening of the jar. I considered that if the lid capped the exterior of the rim instead, the opening wouldn’t lose any space to the gallery and therefore would be much larger.
Forming the Jar Body
Prior to throwing, I like to wedge all the clay I plan to use for the day. I use a stoneware clay body with added grog. The repetition of this process not only allows my mind to focus on the task at hand, but also offers physical fitness to the upper body.
9 Brush on an appropriate design for the form with wax resist over the dried wash.
10 Dunk the jar into bisque slip. Let the slip pool and drip around the resist.
11 Coat the lid in a bisque slip and allow the slip on both pieces to cure for 24 hours.
12 Glaze the interior and exterior with an ash glaze.
Center approximately 7 pounds of clay on a bat (1), and begin opening. Make sure the base is wide enough to be stable and always maintain a cone shape when bringing up the clay (2). Once the desired height is achieved, begin shaping the form with support from a wood or metal rib on the exterior (3). Recenter the rim and smooth it with a chamois, making sure that the rim is tapered inward to give a little leeway in the fit. Allow the pot to set up to leather hard without detaching it from the bat. Next, trim the entire form to reveal the texture of the gritty stoneware body (4). The bisque slip I use is extremely sensitive to the finished surface of the pot, so I often trim the surface to change the slip’s final appearance. Finally, clean up the base with a wooden knife, cut the pot off the bat, and bump in the bottom so the pot will set nicely on a table (5).
Throwing a Cap-Style Lid
Center about 1 pounds of clay for your lid, then open up and pull out to the width of the jar’s opening. The interior diameter of the lid should be equal to the exterior of the jar rim. Next, pull the wall of the lid up. I prefer the wall of the lid to be tall to assure that it doesn’t visually float, because it would be resting on the rim of the pot, but rather rests on the shoulder just below the rim (6). Make sure to compress the interior with a metal rib and recheck the width with calipers. Cut the lid off the wheel and trim it when it’s leather hard (7).
A Handmade and commercially-bought tools and brushes used for slip decoration.
Lattice serving bowl, soda-fired stoneware, slips, glazes, 2016.
Crane plate, soda-fired stoneware, slips, glazes, 2016.
Once the pot is bisque fired, the decorating can begin. Apply wax where the lid and the jar meet on the jar’s upper shoulder, then coat the exterior of both pieces with iron wash (8). I use a stiff high-quality brush (see A) to create a dogwood pattern with wax over the dried iron wash (9). Lower quality brushes don’t work well or last long.
Repeat the same dogwood pattern on the top portion of the lid, leaving the lid’s exterior sides bare to react to the atmospheric firing.
Once the wax dries, submerge the piece into bisque slip, keeping in mind that elapsed time submerged equals increased slip thickness, even more so than with glazes (10). Once the slip has cured for 24 hours (11), coat the interior and exterior of the piece with an ash glaze (12).
All that remains is to fire the piece. I prefer to fire in a soda kiln as it lends the depth and variation to surfaces that I’m looking for. Finally, take your capped jar home and fill it with some homemade baked cookies!
Matthew Krousey received his BFA in ceramics from the University of Minnesota-Twin Cities and is a veteran of Operation Iraqi Freedom. His work has been exhibited locally and internationally, including an exhibition at Sanbao Ceramic Institute in Jingdezhen, China. He is a 2010 Folgelberg Fellowship and 2014 Jerome Project Grant recipient through Northern Clay Center. Throughout the year he finds inspiration fishing the frozen lakes and walking the dense forests of Minnesota. See more of his work at www.mkrouseyceramics.com and on Instagram @mkrouseyceramics.