A porcelain manufacturing technique developed by English potter Josiah Wedgwood in 1775. His ware was typically a blue stained unglazed porcelain with intricately overlaid relief designs of a white unglazed porcelain. The term jasper derives from its similarity to the stone. The manner in which these designs were carved in large size and then reduced by repeated negative impressions of a high shrinkage clay is a matter of amazement for those who have studied the technique. The amount of stain needed in the body differs by color. When raw oxide colorants are employed (e.g. cobalt for blue) the porcelain formulation must be adjusted to compensate for the effect on degree of vitrification, they must also be thoroughly milled to eliminate fired specks. Modern applications of this technique use stains to get much better consistency and color. The ware us burnished after production.
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