Appalachian Center for Crafts

Vince Pitelka, 2016 Glossary of Colored Clay Techniques

Basalt Body: a clay body containing enough metallic oxides to fire to a gray-black or chocolate brown color. Basalt bodies may be fine-grained and smooth, as in Wedgewood black basalt ware, or may be grainy and rough, as in some sculptural works by Peter Voulkos and John Mason.

Burnishing: historically the third stage in pottery decoration in almost every culture, after surface impressing and slip painting. Burnishing allows for a smooth, dense, glassy surface on any clay without the use of glazes. Color intensity is enhanced with burnishing almost as effectively as with the “wetting” effect of a clear glaze, and burnishing gives a satin texture achievable through no other method. Burnishing is generally done at the bone dry stage after re-introducing moisture into the clay with a thin coat of lard, glycerin, shortening, or cooking oil. One the lard or oil is absorbed, the surface is rubbed with a smooth hard object such as a shiny pebble or the back of a steel spoon. After firing, burnished wares are often polished further with pure tung-oil (a wood-finishing oil) or furniture polish.

Clay Marquetry: similar to marquetry in wood. Small pieces of damp colored clays are assembled on a clay back-up slab (with a spray of vinegar water) to create pictorial imagery. Sometimes the designs are improvised during assembly, often overlapping components. For greater precision and pictorial clarity, an original design may be executed on poster-board, which is then cut up into individual templates. The templates are used as patterns to cut the clay pieces from thin slabs sliced from clay loaves with an appropriate clay-veneer-slicer. In either case, after application of marquetry elements, the laminated slab is covered with canvas and rolled aggressively to ensure joining.

Imagery in clay marquetry may be composed of patterned, marbleized, or solid-colored loaves, or often a mix of all three. NOTE: this technique is sometimes mistakenly referred to as “clay murrini” or “clay millefiore,” but both are incorrect. Clay murrini and clay millefiore components are often used in clay marquetry, but the process of using templates to cut clay shapes and assemble an image is unique to clay marquetry.

Another approach to clay marquetry involves laminating patterned or solid colored veneers to a leather-hard thrown or handbuilt piece. Score the surface lightly and spray on a little vinegar water before pressing the lamination into place. To insure proper attachment, cover the lamination with a small piece of canvas, and roll with a rubber roller.

Clay Murrini: colored clay technique adapted from Venetian murrini glass technique. By a variety of methods, colored clays are built up to form a loaf with a pattern or image running continuously through the loaf. Thin layers may be sliced from these loaves and used either as components to construct forms, or as surface decoration over a leather-hard form. See the handout on colored clay

1 loaf construction for murrini variations. NOTE: this technique is sometimes mistakenly referred to as “clay millefiore.” Millefiore, which means “thousand flowers” is just one traditional Venetian glass murrini effect, while the term murrini refers to any image or pattern loaf created by this technique.

Lamination of Colored Clays: Although mentioned in the section on clay marquetry, that technique involves completely covering a surface with laminated imagery. Laminations may be useful for creating surface relief in limited areas, or for numerous other decorative purposes. The surface to be laminated may be wet or soft-to-medium leather-hard. Score lightly and spray on a little vinegar water before pressing the lamination into place. To ensure proper attachment, lay a small piece of canvas over the lamination, and roll lightly with a small roller.

A very interesting approach to surface lamination involves rolling out patterned or solid veneers of clay between layers of plastic wrap. The resulting slab may be as thin as you wish, far thinner than is possible with the veneer slicer. Even when extremely thin, colored clay laminated veneers will give dense, rich colored clay effects. After rolling, when ready to laminate, peel one sheet of plastic directly back upon itself, leaving the lamination stuck to the other sheet. Use that sheet to press the lamination into place on the scored, dampened surface. Peel the other sheet of plastic directly back upon itself, leaving the lamination on the clay surface. If you wish, you can cut the laminations into shapes with scissors while still between the layers of plastic wrap. It is a little harder to peel the plastic away, but well worth it.

Layered Colored Clays: A thin veneer containing multiple layers of contrasting colored clays is applied to a piece, or a piece is constructed out of a slab containing many layers of colors. When the form is leather-hard or bone-dry, the surface is carved, scraped, or sanded away to reveal the successive layers of slip and the claybody underneath. Or, when still soft, the laminated form may be worked from the inside to “dimple” the surface outwards slightly, so that when the surface is scraped, the “dimpled” areas will show concentric circles of the various layers of colored clay.

Marbleized and Grained Surfaces: The most commonly used colored clay technique. Clays of the desired colors are combined and are partially cut/wedged together, twisted, and stretched to create marble (or other rock) or wood-grain-like effects. See the appropriate sections in the handout on colored clay loaf construction. Slices of the marbleized clay can be used in press-molds, slab construction, or clay marquetry. Solid lumps of marbleized clays can be used in pinch-forming and thrown forms.

Neriage: Traditional Japanese technique where colored clay bodies of contrasting colors are sliced and re-combined to build up a loaf with a hard-edged pattern running continuously through it. Layers are sliced off the end of this loaf and pressed edge-to-edge into a mold, usually with a coat of slip between pressed pieces, creating wares with the same pattern showing inside and out. As in clay murrini, the individual slices are often manipulated with the fingers or rolling pin to stretch or distort

2 the pattern. Surface must be scraped when hard-leather-hard, or sanded when dry to remove surface smearing.

Nerikomi: Japanese technique where colored clays are combined to create marbleized effects. May be as surface laminations on a previously thrown or handbuilt form, or may be formed into a cylinder of clay, or pressed into the surface of a cylinder which is then thrown on the wheel to create a vessel. Sometimes colored clays are pressed into the surface before throwing is completed. As with other colored clay techniques, the surface must be scraped when leather hard or sanded when dry to remove smearing. Note: even in Japanese pottery literature there is much confusion over the distinction between the terms “nerikomi” and. “neriage,” and they are often used interchangeably.

Pate-Sur-Pate: (translates paste-on-paste, or clay-on-clay) European technique of laminating colored clay appliqués or repeated layers of slip decoration on contrasting colored clay body, creating raised relief into which detail is carved. Best-known examples are English Wedgewood jasper-ware (usually white decoration on blue claybody). Some "cameo" jewelry items are made using this technique.

Slip-effects: The most important use of slips or slurries in colored clay work is as the standard joining material, as is the case in all ceramic work. In this case, however, the slips or slurries may be colored and may be used as a decorative medium as well. Always add a little vinegar to any slip or slurry used in colored clay work. When joining pieces or slabs of colored clays, you have the choice of using a colored slip which matches the adjoining clays, or using a contrasting slip, which will create a very fine line of contrasting color. This may be used to great advantage whenever a very thin line of color is desired. Also, when combining stretched murrini loaves to create a composite loaf, a layer of slip will fill all the gaps between the individual stretched loaves, and can provide a line of contrasting color through the pattern. Finally, white or colored slip may be used as the ground upon which to apply colored clay sprigging or appliqué.

Sprigged Colored Clay: A technique using very small coils, balls, or press-molded pieces of clay applied to a contrasting claybody or slip ground. Sometimes involves a single color contrasting with ground, but often employs many shades of colored clay. Sprigs may be hand rolled, or may be extruded from a Kemper mini extruder. After application, surface may be paddled to slightly flatten sprigs, or may be rolled to make them flush with the surface.

Swirlware: Effect created when combined colored clays or marbleized clays are thrown on the wheel, giving the expected swirling spiral patterns. Although a bit of a cliché in ceramics, contemporary artists like Dick Studley and Ban Kajitani have proven that there is still room for innovation with colored clays on the wheel.

In one approach, start with a lump of marbleized clay, which is centered and thrown in a conventional fashion. This works best with a fairly coarse marbleized loaf, with highly contrasting colors. Another approach involves a custom-built colored clay lump. The easiest method is to form

3 an equal number of cylindrical lumps in each of the colors you wish to use, cut them all into pie slices, and separate and recombine them, mixing the colors. The lump is then gently tamped on the table surface to connect the clays, and thrown in a conventional fashion. Or, cut a cylinder vertically in half, insert a thin slice of colored clay, reassemble the cylinder, turn it, cut it again, add a slice, and repeat as many times as desired, tamp the lump, and then throw in a conventional fashion. Finally, you can partially throw a form with a single color, and then press contrasting colored clay wads or coils into the surface of the vessel and finish throwing. In all of these techniques, the colors will smear together on the surface during throwing, and the vessel will have to be scraped when leather hard or sanded when dry to bring out the colors.

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