Why bone china is so demanding
Short clay, a high first firing, a narrow window and big shrinkage. Each is manageable; together they make bone china hard to do well.
Ask a ceramic engineer why bone china costs more than porcelain and the answer is rarely the raw materials alone. It is the yield: how many pieces survive to be sold.
Five challenges
A “short” body. With about half the mixture made of non-plastic calcium phosphate, the clay is less forgiving to shape, and unfired pieces are fragile to handle.
A high first firing. The body is taken to vitrification before glazing, at a temperature where it softens enough to sag.
A narrow firing range. Small deviations distort pieces or leave them under-fired.
Large shrinkage. Moulds must anticipate it precisely, shape by shape.
Several firings and strict selection. Decoration often needs its own firing, and each firing is another chance for loss.
What has changed
Modern kilns, electronic control and quality systems have made consistent production far more achievable than in the age of the bottle kiln. That is a large part of why bone china is now made on several continents. It has not made the material easy.
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