Bone china is an English variant of porcelain that replaces part of the standard hard-paste mixture with bone ash, lowering the firing temperature and improving chip resistance at some cost to translucency compared to a well-fired hard-paste body.
Bone china's bone ash (calcined, ground animal bone, chiefly calcium phosphate) acts as an additional flux and structural component alongside kaolin and feldspar, letting the body mature at a lower temperature than true hard-paste porcelain needs. The resulting body is notably strong and chip-resistant for how thin it can be worked, which is part of why bone china became closely associated with fine, thin-walled tableware, though it is generally a little less translucent than a well-fired hard-paste body at an equivalent thickness. The traditional formula runs roughly 50% bone ash to 25% kaolin and 25% Cornish stone (a feldspathic flux), though how much bone ash actually qualifies as "bone china" is a matter of real regulatory definition, not just tradition: the UK's legal minimum is 30% calculated bone phosphate, while the US minimum is lower, at 25%.
Bone china developed in England during the wave of porcelain factories that followed the 1712 publication of d'Entrecolles' account of Chinese manufacturing methods (see porcelain's own history), as English manufacturers worked out their own distinct variant using bone ash rather than reproducing the Chinese formula exactly. Josiah Spode is generally credited with defining the improved bone china formula around 1789–1791, refining it into essentially the form still produced today, though no surviving documentary evidence (dated pieces, recipe books, diary entries) records the exact date of the invention itself. Spode's son, Josiah Spode II, is credited with successfully marketing the material commercially. It went on to become the standard formula for most English fine china manufacturers.
Bone china's combination of strength and a lower firing temperature than hard-paste made it commercially attractive for tableware manufacturing specifically, where chip resistance under everyday use matters as much as appearance. It remains the standard porcelain formula for most English and many other Western fine-china manufacturers today, distinct from the continental European preference for true hard-paste that persisted at factories like Meissen and Sèvres.