When the traders traveled the Silk Road to China and brought back Chinese porcelains, most of Europe was still making crude earthenware pottery. After all, in Europe the royal courts used gold and silver. But in China the courts used porcelain, and were centuries ahead of the Europeans in ceramic technology. The cobalt blue on white Ming Dynasty vases are still imitated today.
So when these Chinese ceramics began to be imported to Europe, they were nicknamed “china,” as that was from wince they came. Shortly after than, the industrial revolution began in Europe, and the demand for “china,” or porcelain, was a great market for mass production.
Unfortunate, porcelain was very expensive to produce, as it needed to be fired so high; in excess of 2500 degrees Fahrenheit. And, when firing clay pots that high, many warped and cracked and were unmarketable. Back in China, at the ancient kiln sites, there where huge mountainous piles of shards or broken pots, that had been destroyed in the firing. This sort of loss was no acceptable when one’s goal was mass production.
And so they found a way around it. They added a mineral to the clay that would lower the temperature at which it would fuse in the kiln. They made molds, called saggars, and the unglazed pots where placed in these molds and then fired. The sagger prevented them from sagging. After that firing, the glaze would be applied and they were fired a second time to a LOWER temperature. This is backwards from how it is usually done. So the glaze didn’t get a good molecular hold on the clay, and would chip very easily. But this whole thing lowered losses considerably as well as lowering the cost to mass produce the dishes.
And what was the mineral they used to lower the temperature the clay would fuse at? Calcium. Calcium is what is called a flux or melting agent. It lowered the temperature by as much as 800 degrees. And where did they get the calcium? Cattle bone ashes……. bone china. Yep…. actually a cheaper product.