Horizontally Layered Colored Clay: A Ceramic and Geologic Process Allan Kluber

Appears in the January 2021 issue of Ceramics Monthly.

I had been away from ceramics for 30 years when a trip through Southern Utah, with its astonishing rock formations, led me to return to clay. The initial sculptural work focused on the connection between ceramics and those geologic formations I had observed. Then my 50-year-old functional pottery roots reasserted themselves, and the geologic reference became embodied through the horizontal layering of colored clays in the vessel walls. When these layered slabs were cut, stacked, and rearranged, in a way much like the earth’s surface over time, a rich and vital new way of working began to evolve.

A year later, I was asked to substitute for two weeks in an ongoing colored-porcelain handbuilding class at Clay Space in Eugene, Oregon. That’s when I was faced with the question of whether I was willing to share this way of working with others. On the one hand, I was reluctant. It felt like I would be giving away what I had worked hard to develop. But on the other hand, wouldn’t it be interesting to see what others could do with this process? I decided to share freely. The result was a creative outpouring far beyond what I could have imagined.

The horizontal layering of colored clays into a slab is not unlike mille-feuille pastry. Beginning with a single layer of each color, one is placed on top of the other, then this layered slab is cut into four pieces and stacked again, from one to four more times. These layered slabs are then formed to become the body of the pot. This process differs from neriage and nerikomi, where colored clays are marbled in the clay wall or sliced from an arranged block and then attached and formed to create a vessel. The horizontal layering of the clay is an analog to the geologic layering of differing materials over eons and their subsequent formation into rock. As in geology, this layering is not visible from an uninterrupted surface, but when the surface is disturbed or cut apart, the interior complexity of the pot’s wall or geology is revealed.

Note that while I share the basics of this technique, including the choices I make at different junctures, making different decisions at each point could lead to many rich possibilities.

Beginning the Layering Process

I begin the process with controlled slab rolling using a rolling pin. In keeping with the geologic metaphor, I prefer to allow the slab edges to remain in their natural, uncut stage. An analogy in furniture making is the incorporation of the live, or uncut, board edge into the final piece, a style that was pioneered in the 1960s by George Nakashima. In order to roll out a square or rectangular slab, don’t use the rolling pin to flatten the clay completely to the slab’s end; instead, stop rolling before the end, leaving a thick edge. Then, turn the slab 90 degrees and roll it out again, pushing the thick edge toward the two furthest corners. That roll also stops short of the end, leaving a bulge to again be rolled to the corners in the next pass, which is also done after turning the slab 90 degrees. This process is repeated until the slab is the desired thickness and shape. Tilting the rolling pin up or down on the bulged edge can influence the movement of the clay in the desired direction. This takes some practice, but is not difficult.

The Foundation

The four-layer, two-color slab is the foundation of the layering process. Begin with four parts of a base clay (usually white) and roll it into a square slab. Then take a piece of the second clay (one part or one-fourth the weight of the first), and roll it into a square somewhat smaller than the bottom slab. Place the smaller layer on top of the larger, revealing the bottom layer around the edge and roll the two slabs together. Cut the rolled slab into four pieces (1) and stack them on top of each other (2). Turn the stack over and roll it out, keeping it square (3). By turning the slab over when it is rolled, the top layers are pushed out over the bottom ones to further reveal the layers around the edges. Turn the slab over. It is now ready to form, or to do additional work on.

The process for making multi-colored layered slabs begins with the top two layers, which are first rolled together as in the two-color slab process. This slab is then placed on top of the next, larger bottom slab layer. Typically I make each layer four times the weight of the one above, so the ratio of weights of a three-layer slab from top to bottom will be 1 to 4 to 16. Usually I make the top layer a strong color, the middle layer a more pastel color and the bottom layer plain white clay. Different color and size proportions will create very different looks.

Cutting and Overlapping a Layered Slab

To reveal the interior of the layered slab, cut off a piece with the knife held at a sideways angle (4), creating a beveled cut. The cut can be straight or curved. The greater the knife angle, the broader the exposure of the interior layers. Cut as many pieces as desired and then join them by overlapping the upward exposed edges over the downward exposed ones (5). Cover the slab with plastic wrap to avoid smearing and roll the pieces together (6). Typically this cutting and overlapping is done when the slab is smaller and thicker than the finished slab so that the final rolling can be to the desired size and shape. A joined slab can be cut, reattached, and rolled together again to develop a more complex pattern.

A Geologic Reference and Functionality

Most of the time I cut the slab in four and stack the original layered, colored-clay slab just once resulting in a four-layer slab. Sometimes I cut and stack it again (7, 8), resulting in a 16-layer slab. Occasionally I repeat this two more times, which results in a slab of 256 layers. When this is rolled out from the back side, the multiple layers are revealed encircling a small, solid center. The geologic reference becomes more fluid on the surface.

Flipping Sections and Cutting Off Protrusions

When the layered slab is cut apart into three or more sections, alternating sections can be turned over before being rejoined. This brings pieces of the bottom side of the slab to the top side (see 15, 16). When the slab is formed into a vessel, parts of the inside are now on the outside. A rolled slab of flipped pieces can be cut apart a second time at a different angle into pieces that are alternately flipped again, adding complexity.

If small pieces of clay are placed on the back side of a layered slab (9), they will create protrusions when the slab is turned back over. If these protrusions are cut off with a very thin wire (10), the layers are revealed. This cut-off piece can be discarded, but I like to make use of it, either by flipping it and rolling it into the slab’s surface or attaching it right-side-up to the slab and cutting it off again using thin slats (11). This attaching and cutting off the remaining protrusion can be done multiple times until the entire protrusion is used up. This results in a diminishing series of the original protrusion’s shape and interior pattern.

The shape of the piece of clay that is placed on the back of the layered slab will be reflected in the protrusion. Specific shapes (12), either cut out or press molded, can be placed on the back of the slab. If using a press mold, once the slab is flipped right side up, the mold can be used again to press over the protrusion (13) so that it is the same shape as the piece that was placed on the back (14).

Addressing the Rim

My preference for leaving the natural edge of the slab rather than cutting it creates a problem for the lip of a drinking vessel, which, in order to function well, needs to be straight and even. I have dealt with this by making drinking vessels in pairs from one layered slab cut lengthwise into two pieces (15). Once a cylinder is formed, the cut edge forms the straight rim of the two vessels (16). This pair, if joined lip to lip, will show that the two cups were originally one slab that was cut apart.

The Layered Slab as an Interior Body Metaphor

I have focused on this process as an analog to geologic processes. To the extent that a vessel is a natural metaphor for the human body, this layering can become another metaphor for a person accumulating experience over time. Experience does not often show on the surface, but if one gets below the surface, it can be seen. Cutting the slab reveals the pot’s/person’s interior layers and complexity.

Horizontally Layered Colored Clay Workshop

I have led two workshops on this layered colored-clay slab-building process at Clay Space in Eugene with a format of five classes spaced a week apart and a glaze firing scheduled each week. I found that this is a very accessible process with a short initial learning curve. Beginners are able to quickly master the basics and make meaningful work after a few classes. Potters with many years of experience can explore a new process to use for expressing their voices. The participants demonstrated that there are many rich applications and variations.

This feels like new terrain that is little explored. I hope there will be others who will find this a fertile process that can serve their ideas, interests, and feelings. I look forward to seeing what others will do.

1–16 Photos: Jane Souzon.

the author Allan Kluber makes pots, does volunteer mediation, and helps struggling first-grade students learn to read in Eugene, Oregon. More information on Kluber’s ceramic work past and present, including step-by-step process sheets, can be found on his website, allankluber.com.