Posted in Reference
I've always thought that tea tastes best in cups made of bone china. They look and feel the absolute pinnacle of refinement. However, I had never thought to question the name of this type of china, just took it for granted and drank my tea. So I was a little surprised to learn that it's named for the bone it contains, and indeed some vegetarians and vegans will have nothing to do with it. Just in case there are others out there as slow on the uptake as me, I shall explain a little about the processes involved in its manufacture and something of its history too.
The ingredient that sets bone china apart is bone ash, produced by the calcination of animal bones and it is this that gives it such strength, its white colour and its translucence. The animal bone is first processed to ensure that no meat is left and then treated to remove glue. The remaining raw bone is heated to around 1,000°C, which both sterilizes it and changes its structure to make it fit for the purpose of manufacturing bone china. It is then ground up with water and added to china clay and china stone. The resulting composition is first fired at 1,200-1,300°C, called biscuit firing and then at 1,050-1,100°C. The second firing is also known as glost firing. The resulting material is more resistant to chipping than fine china or porcelain and its high strength is what makes it possible for it to be made into thinner, more delicate products.
The first developments towards bone china were made in the mid 18th century by Thomas Frye, whose East London factory wasn't too far from local cattle markets and slaughterhouses. Thus, it was easy for him to obtain animal bones. He used up to 45% bone ash in what he termed his fine porcelain, but despite its high quality it did not become commercially successful until further developments were made by Josiah Spode towards the end of the 1700s. His method differed in that he removed all raw materials from the bone prior to calcining it. His formula was 6 parts bone ash, 4 parts china stone and 3½ parts china clay and this is still the commonly used formula today. Other companies such as Minton, Wedgwood and Coalport soon noticed Spode's success and started to produce their own ranges. However, as a lot of early produced bone china was unmarked, it can be hard to distinguish pieces. You may even have in your possession a rare piece and be blissfully unaware as you chase your peas around the plate or take a swig of Earl Grey. Perhaps a visit to the 'Antiques Roadshow' could pay dividends, but until it comes to town you may as well go and enjoy another cup of tea in your best cup and saucer.