Explanation of terms used in descriptions of my work
Below is somebasic information about clay techniques, for those interested in better understanding how each the work is made.
How my pots are made
For most of my work, I use a potter's wheel to "throw" the form. This method requires lots of practice to master, but the result is a rapid formation of strong, concentric forms. For larger work, I throw a piece in sections to be joined, or add a thick coil to a thrown wall and throw it some more. Often, I will add thrown or hand-built pieces, such as handles, spouts, etc. when the pot is leather hard. I also like to deform and reshape thrown pieces when making sculptures. When I'm done reshaping, it is often difficult to tell that the work began on the wheel (e.g., view my Tree Trunk abstract sculpture image). Some pieces are made from slabs, using either a rolling pin or a slab-roller I recently bought. My tiles are started as slabs, and sometimes I modify them adding texture and relief. Another handbuilding technique I use is to add coils or 'pinch pieces" to build up a form. I recently bought an extruder, which uses a piston to compress clay through dies to form specific shapes. This is a realm I'm just beginning to learn. Sometimes I use a polished river stone inside a wall as an anvil and beat it from the outside with a wooden paddle, thinning, strengthening, enlarging and reshaping the form. |
How my pots are fired
Ceramics is a slow process that takes lots of time at different stages. I may be able to throw the basic form in a few minutes, but this is the least of the time involved. Once work is formed, it must be left to dry partially, to what is called "leather hard" condition. At this stage, the walls are more firm, but still contain moisture and can be reshaped and joined to other similar pieces. Conventional functional pots are trimmed at this stage, and handles, spouts, etc. are attached. Then the pot must slowly dry completely, which takes days or weeks depending on the piece and the weather. Then work is bone dry (feels warm when placed against my cheek), this "greenware' is loaded into a kiln for the bisque firing. Until a pot is bisqued, it is very fragile and if submerged in water, can be recycled to its original malleable state. The bisque firing removes all water chemically bonded to the clay particles, leaving a porous pot that will draw water form the glaze, which is applied with a brush, by dipping pouring, or spraying. Then the work is refired to a higher temperature, at which the clay vitrifies and becomes strong and non-porous, while the glaze melts and adheres to the surface. |
Oxidation firing
Pots that are fired in an atmosphere with ample oxygen, such as in electric kilns, are oxidized. At present all my work is fired in electric kilns except for Raku work, as I don't have a reduction kiln available to me. In the past, oxidation glazes were not very interesting, but by combining multiple glazes, with overlays, etc., oxidation glaze results can be as interesting and unique as reduction. I am using rutile glazes such as those developed in Mastering Cone 6 Glazes to get wonderful results I never thought possible in oxidation. |
Reduction firing
Kilns that involve combustion (burn wood, oil, gas, propane, sawdust, etc.) and limit the available oxygen are called reduction firings. In reduction, the burning material is starved of oxygen from the kiln atmosphere so in order to burn, it takes oxygen from the clay and glazes, thereby reducing them. Reduction is what makes many Raku glazes so dramatic. The same glaze may look completely different when oxidized than when reduced, for example, copper turns glazes green or blue in oxidation but red in reduction. |
Oxidation or Reduction Glaze?
This is a trick question, but with a point. I used to find that many oxidation glazes lacked the qualities I prefer with reduction firing, and were just plain and boring. However, as this large fruit bowl shows, one can get exciting results in oxidation too. This pot was fired to cone 6 in an electric kiln using 'Variegated Slate Blue' glaze formula from the Mastering Cone 6 Glazes book (Roy & Hesselberth). A combination of including rutile in the glaze to form microscopic crystals, and firing with a controlled slow cooling program allows for development of very reduction-like results. Layering two glazes allows for even more dramatic effects. I'm no longer as frustrated about not having a reduction kiln to use.
Raku firing
Originally developed centuries ago in Japan for ceremonial tea bowls, in the U.S., Raku has evolved to connote a rapid lowfire kiln in which pots are heated to about 1,600° F, removed red hot (with tongs and protective gloves, etc.) and reduced inside a can containing combustible material (like leaves, paper, sawdust, pine needles). After only a few minutes in the reduction chamber, the slightly cooler pots are carefully brought out into the air and cooled with water to prevent reduced glazes from oxidizing. It is an exciting and dramatic experience, and compared with most ceramics firings which take days to load, fire & cool a kiln before the results can be seen, with Raku I can fire a load every hour, and adjust the glazing and firing based on the prior round results. Sometimes I fire 7 loads in a day in a kiln I made from a garbage can. Another bonus of Raku is that it is much easier to do with a group of people, and the experience for potters and non-potters who assist at Raku parties is a thrill! Raku pots are fragile due to the low temperature firing and the shock of rapid cooling and the clay is porous, so these are not suitable for dishes, and the like. However, they make great sculptural and decorative pieces. Warning, because Raku and other lowfire pots can absorb water, they should not be left outside during Winter as the freeze-thaw cycle, with snow moisture can result in the pieces disintegrating. |
Naked Raku
No, the potters don't fire these pots in the nude (although many a joke along these lines has been shared). Instead, it is the pot that is naked, meaning left unglazed. Instead og glazing the pot, after the initial bisque firing, it is dipped in a specially mixed clay slurry (called "slip") which will not adhere permanently to the piece. The pots are fired in a Raku kiln much as described at left, and the heating causes the slip to crack and peel. When the pot reaches temperature and is removed to the reduction chamber, the carbon from the burning material is absorbed by the clay body not covered by the slip. Once fully cooled, the remaining clay slip is peeled/washed off, revealing fascinating patterns of black, gray and white clay. Potters can exert some control over the black patterns by using wax and other masking methods to leave specific areas without slip, and these will be the blackest of all once the firing is completed. Raku pots are fragile due to the low temperature firing and the shock of rapid cooling and the clay is porous, so these are not suitable for dishes, and the like. To hold water, Raku vases must be sealed on the inside. Warning, because Raku and other lowfire pots can absorb water, they should not be left outside during Winter as the freeze-thaw cycle, with snow moisture can result in the pieces disintegrating. |
Horsehair post-firing
Another variation on Raku is to leave all or part of the pot surface bare (unglazed). When the pot reached 1,600°F, it is removed and placed on a flat stone to cool in the air. Before it has had time to cool very much, strands of horsetail hairs, feathers, pine needles and other delicate combustible materials are placed on the hot surface, where they immediately burn. This leaves black lines and smoky gray shadows on the surface that can be very beautiful. My thanks to the local stable owners in Putnam County who generously permitted me to collect hair from their grooming brushes. |
Sawdust & Pit firing
Still another low temperature alternative firing process I've experimented with involves putting unglazed pots in a pit or can filled with sawdust, wood shavings, wood chips, or dried cow manure. Then the top of the combustibles is lit and the pile slowly burns to the bottom. This is a traditional method used for millenia all over the world. Traditional Navaho and other Southwest native potters still use this to make their beautiful blackware and redware. For a shiny surface, the pots are painstakingly burnished with the back of a spoon or a polished river stone. Sometimes metal oxides like copper carbonate are added to expand the color range. |