Pour a coating layer of slip over the slab, covering the entire exposed surface, allowing the excess slip to drain off (figure 1).
Evidence from original examples like the Staffordshire or Midlands Dish suggest that the lines were laid down in very specific, proscribed patterns which runs contrary to the suspicion that the marbling process used a more random application of slips. The edge of the original example is the key to determining the original configuration of the white slip lines. There is more white at the edges and patterns loop back from this point all around the piece, which indicates the series of lines was trailed on, one at a time, in a continuum within the confines of the slab disc, doubling back for each consecutive line (figure 3). This observation was critical to deciphering the trailing process employed by the 18th century Staffordshire potters to achieve this specific marbling technique.
After the slip lines are systematically applied, the clay slab, still supported by the bat, is then tipped and rotated using gravity to coax the slips to flow (figure 4). This process will create a pattern of swirls (figure 5). If the slip is too watery, the lines will run and blur. If the slip dries too quickly, the slips will not flow properly. Two conscious aesthetic and practical decisions have to be made: (1) how much time can be expended before the wet slips stop flowing; (2) how to judge when to stop before the lines of color lose their separation and become muddy. Because both slips tend to firm up quickly, the elapsed time for joggling is usually thirty to forty-five seconds.
|The now marbled slab is set aside to allow the slips to dry further. Before the vessel is formed, the slips must be allowed to set up to prevent marring of the marbleized surface yet the slab and the newly slipped surface must remain pliable. If the slab becomes too dry, it will crack. If the slips are still too wet, the slab will stick to the surface of the mold. After the slips are no longer tacky or wet to the touch, the entire slab, which is still plastic, is removed from the bat and placed over a “hump” mold surface down and pressed into shape (figure 6). These molds were typically made of fired clay although a plaster one is being shown here. Allow the dish to dry further to a leather hard stage. The irregular edge is trimmed with a knife to form a completely circular form and the rim is then crimped or pressed with a coggle wheel to create a pattern. The molding process helps flatten the slips and after glazing, the surface is smooth.|
As a ceramic artist my methodology is integral to my study of early ceramic techniques and the process of experimental archeology, using objects and fragments from ceramic history to rediscover the mysteries of the processes and materials used to create these wares. Obviously in the 21st century there are numerous commercially available materials to create a spectrum of palettes and glaze surfaces. For my purposes, however, I have chosen to develop all my own slips and glazes often using indigenous clays, metallic oxides, carbonates and sulfates and basic raw ceramic materials to create all of my glaze formulas as needed.
Suggested Clay and Slip
The piece I illustrated is a dark brown/black slip ground with a white slip trailed on top and the gold color of the finished piece comes from the addition of iron to the low temperature clear glaze.
There are many commercially available clear glazes and you can add a commercial yellow stain for the effect. I use iron oxide to give my own cone 04 formula its yellow gold hue to closely resemble the lead glazed Staffordshire slipwares. As I do not use lead on functional wares, I often use more temperamental ingredients that have small firing ranges and require a lot of experience in glazing and firing, so I am not including those formulas as they are not user friendly nor safe.
It is important to test fire new slips and glazes. I find my small test kiln invaluable and I will often take it up slowly and down fire it to more closely resemble the conditions in the large kiln. All my pieces are fired in Electric kilns but they do not self-fire and I do not use kiln sitters as my glazes are finicky and require manual manipulation of temperature.
11. Top: Michelle Erickson, London Slipware Charger #1, 15 ½ inches in diameter.
|12. Above: London Slipware Charger #2, 15 ½ inches in diameter.|
In the case of most English flatware, the marbled or combed decoration is created before the form. Marbleizing on hollow forms takes place, however, after the vessel has been created, usually by throwing. The ground slip is either poured over the vessel or it is dipped into a container of slip. Contrasting colored slip is then trailed on, again in a systematic fashion. The vessel is then tilted and rotated to control the gravitational flow of the slip creating a variegation of the wet slips.
In addition to marbleized patterns, the same technique, without the joggling, can be used to create distinct images using contrasting slip. Slip is poured onto the surface then a design, image or pattern is trailed onto the wet surface. The slipware chargers above are examples of this technique.
Michelle Erickson has over 20 years experience in working with 17th- and 18th-century reproduction pottery in addition to her considerable contemporary work. She produces reproductions for organizations such as Colonial Williamsburg, the National Park Service, Parks Canada, the Museum of Early Southern Decorative Arts, the Philadelphia Museum of Art and Historic Deerfield museum. She is a partner in the business, PERIOD DESIGNS in Yorktown, Virginia, an innovative firm specializing in the reproduction of 17th- and 18th-century decorative art. For more information, or to view more of her work, visit her website at www.michelleericksonceramics.com