Bob Green has been a potter for thirty years. Currently, he lives in western Massachusetts on an old dairy farm with his wife Karen Totman, and their pet Miles, an Australian Shepherd.
Bob’s burnished vessels are thrown using porcelain clay. This very smooth white clay lends itself to the burnishing process. This process of burnishing terra sigillata is a technique Bob worked on while in graduate school. He was looking for an unglazed surface for his clay pieces and became very interested in early Greek and Roman pottery of the 5th century BC. Green realized that the use of a clay slip for sealing and shining the surface of pots was a common practice for many cultures such as Native American, as well as potters’ of south and central Americas, just to mention a few.
The first time the pot is burnished a coat of baby oil is rubbed onto the surface of the pot and polished; this produces a smooth slightly shiny surface.
The second burnishing involves the thin application of a clay slip called terra sigillata [which is Latin for Earth Seal]. Once the terra sigillata is applied to the smooth bone dry pot it is burnished a second time with a piece of fleece.
A high gloss starts to develop on the surface of the pot. This process of burnishing terra sigillata is a technique Bob worked on while in graduate school.” I was looking for an unglazed surface for my clay pieces and I became very interested in early Greek and Roman pottery of the 5th century BC. I realized that the use of a clay slip for sealing and shining the surface of pots was a common practice for many cultures such as Native American, as well as potters’ of south and central Americas, just to mention a few.”
Once the pot is burnished it is bisque fired for strength. The bisque fired porcelain is very white and shiny, but still porous. Each pot is then placed in a saggar or container which is made of bricks or clay. The pot is then carefully surrounded with hard wood chips, kosher salt and clay oxides. The saggar is sealed with the pot inside and fired again to about 1900 degrees Fahrenheit.
The next day the pots are unloaded from the saggar cleaned and gently buffed revealing a beautiful surface obtained from the smoke and fumes trapped in the saggar with the porous pottery. While these results vary from piece to piece some control is obtain by the way the saggar is loaded and placement of organic material surrounding the burnished pot.
Raku is a sixteenth century Japanese pottery firing process which is closely associated with Zen Buddhism and the Tea Ceremony. “Raku for me is a way of staying connected with my work during the firing process.” Bob’s raku is fired in a small gas kiln to about 1900 degrees Fahrenheit.
Once the proper temperature is reached the kiln is opened and the glowing glazed pots are carefully pulled from the kiln using metal tongs. The hot pots are placed in a nest of hard wood chips; upon contact the heat of the pot ignites the wood and the pots begin to cool in the smoky fire. The pots eventually are completely covered with wood chips and the mounds of wood covered pots smolder.
Occasionally the mounds are uncovered exposing the still very hot pot to the cool air and then they are recovered with dry wood chips; by doing this a crackle pattern forms in the glaze surface, this pattern becomes very black from the carbon of the burning wood. The crackle pattern is only on the glaze surface and does not damage the pot. Bob also fires raku with matte glazes. The matte fired raku is fired to the same temperature and also cools in hard wood chips.
“I’ve learned through trial and error that by dampening the wood chips I can influence the color of the glazes. I dampen the wood with a specific amount of water per five gallon bucket of wood chips.” The matte glazed pots are removed from the kiln in a similar manner as previously described, but rather than exposing the hot pots to the cool air these pots are cooled in the dampened wood for about a half an hour. Upon uncovering they are sprayed with water which quickly cools the pots and freezes the color of the matte glazes. These matte pieces are often fired multiple times in this manner.” I believe that in multiple firings of matte glazes richer colors are obtained.” “My raku firings are done outside during the heat of the summer as well as cold of the winter it all makes me feel alive and involved with my pots.”