Crafts During the last part of the 19th century, it was discovered that slip for casting ceramic ware in plaster molds could be produced using about 30 parts of water to 70 parts of clay, if an electrolyte were added to the mixture. This electrolyte, usually in the form of sodium silicate, soda ash, or a combination of the two, dispersed the clay particles, which resulted in a usable, fluid slip with a lower water content. The addition of a dispersing agent to clay and water is called "de-flocculating." The excellent prepared slips we enjoy today are produced in this way; however, they also contain slightly more than 50% common talc, which gives the finished pieces a white color and a wider firing range.





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January 7, 2009