One of the joys of making ceramic vessels is that you are not restricted to only one form of manufacturing. During the fourteen years Bison has been in Canberra we have utilized three main production methods. We have thrown many of our pieces individually, used a hydraulic press for our flatware, and now are creating a new slip casting division. Generally you can throw objects on the wheel when they are simple round forms. Pressing is done to give consistency and strength to objects which are stacked such as plates. Slip casting is generally utilised as a means of producing forms which have irregular profiles or attachments. This would include such shapes as oval or rectangular plates, jugs and teapots, or objects such as candlesticks or lidded forms.
Slip casting involves the use of professionally crafted plaster molds. We pour liquid clay, the same body as we use for throwing on the wheel, into the molds and allow them to form. After they have attained the correct thickness we trim the excess off and then open the molds and remove the cast forms. Once they have had some time to become firmer we then turn them on the wheel and form or carve spouts by hand. We prefer to use two or three piece molds as they offer greater quality in terms of the shapes they produce. We also ensure that the weight and finish of each piece is checked before allowing them to progress to the glazing/firing stage.
The above image illustrates new holds banded for pouring. I'll show some samples of poured pieces in an upcoming post. Image: Brian Tunks