U.S. Manufacturing of Bone China
Built in 1989, the Lenox Kinston (N.C.) Plant is the only fine bone china factory in the United States. The 218,000-square-foot plant is situated on 40 acres. Its unique manufacturing capabilities include enamel dot, etch, color and microwave metals.
The Kinston plant produces some of the most sophisticated fine china patterns in the world. Among these are nine of the top ten Lenox patterns. It was also this plant that manufactured the Bush White House China.
The Kinston plant uses an average of 4 million pounds of clay each year. The plant can produce 15,000 to 20,000 pieces of china daily.
Lenox china produced in Kinston has received a number of awards from the Society of Glass and Ceramic Decorators for artistic design.
Four main proceses are involved in creating china: Clay making, Mold making, Glazing and Decorating.
Dry raw materials are mixed with water to form a slurry. These slurries, stored in huge tanks, will later be blended together to form the final mix and slip. Five main dry ingredients go into the final mix: bone ash, china clay, ball clay, flint and feldspar. These raw materials are both domestic and imported products.
Lenox creates two colors of bone china, white and ivory. Although certain additives or pigments are used to create the ivory color in the finished product, in the slurry state, both clays are slightly gray. In order to tell them apart, the ivory mix is tinted with green vegetable dye, which will eventually burn out in the kiln.
During the clay stage, which is any time before bisk firing, all scrap clay that hasn't been contaminated by debris can be reclaimed. Products made in Kinston are 80 percent virgin clay and 20 percent reclaimed clay.
After the final mix has been prepared, it is filtered to remove air and water - the moisture level is reduced to about 20 percent. Final mix left in a liquid state is referred to as "slip."
The sheets of clay that are formed in the filter press are then passed through an extruder to remove more air and change the flattened squares to chalk-like tube shapes known "pugs," weighing about 30 pounds. Molds are used to transform the pugs and slip into china pieces.
Large metal master molds and plaster - which draws out moisture from the clay - are used to make production molds. For dinner plates, the metal master molds look like two hubcaps sandwiched together.
To create a production mold, large bags of plaster are mixed with water and then funneled into a big mobile bucket that hangs overhead. The metal master molds are spraying with a soapy mixture that later will help release the production mold.
Two people fill the metal molds with plaster - one pours while the other spins the mold to distribute the plaster evenly. It takes about 20 minutes for the plaster to set. The metal mold is tapped with a rubber mallet to loosen the plaster production mold.
Air hoses are used to clean out the metal molds. Approximately 300 molds are made in this factory every day. Each plaster production dinner plate mold is used about 100 times, while molds for serving pieces and more intricate items can only be used about 10 to 15 times.
Breaking the mold: The formation of a china plate
The forming operation, or pug molding, starts one of two jiggering units, either for white china (gray pugs) or ivory china (green pugs). The pugs are pushed through an extruder to remove any remaining/excess air. A giant slicer cuts each pug into several clay discs.
Each clay disc is placed atop a plate mold that begins to rotate. A jigger head hovering above also starts to rotate, and presses down. A scraping tool cuts off excess clay from the rim of the newly formed greenware plate. (Raw clay pieces that have not been fired in the kiln are called greenware.) The excess clay shoots down a conveyor belt to a recycle bin. This reclaimed clay is blended with water to create a slurry that will go into a batch of final mix.
The greenware plates are passed through a mold dryer, then removed from the mold and passed through a second dryer. By now, the clay's moisture level has dropped from 20 percent to 0.5 percent. The plates move through a finishing machine where damp sponges smooth out the edges.
Workers inspect each plate as it leaves the finishing machine. The plates are placed on setters, which can withstand the kiln's extreme temperatures, and are stacked on metal racks. At this point, the plates are still fairly malleable (they can bend). The setters ensure that the plates maintain their shape in the kiln, where they become what's known as whiteware.
Casting of bone china
Separate machines mold cups, mugs and small bowls. In the casting area, 18 small lazy Susans sit hold 18 casting molds. Three hoses hang from the ceiling: one for air, one for white clay and one for ivory clay. These hoses are used to fill each mold with liquid clay, or slip. The slip then sets for 10 -15 minutes. The excess slip is poured out, and the mold sits for about another 10 minutes. The mold, which is in several pieces, is released, leaving seams along the greenware where it fit together. Workers use damp sponges and finishing knives to remove the seam marks.
Handles are affixed, by hand, to each freshly profiled cup. These cups are then passed to a finishing area. Using small finishing knives, water and sponges, workers smooth out the lip and foot of each cup and make sure the handles are securely attached. The finished cups are placed on small setters, called chums, and stacked on racks headed for the kiln.