Bone China clay is made from 50% bone ash, 25% china clay (kaolin) and 25% China stone (feldspar rich granite). The first person to develop what become known as bone china was Thomas Frye at his Bow porcelain factory near in East London in 1748. Around this time fine porcelain was made in China and imported which was costly. So Frye tried to develop his own fine porcelain and added 45% cattle bone ash which he sourced at local cattle markets and slaughterhouses in Essex. He called it ‘fine porcelain’ but although in terms of quality it rivalled imported porcelain, the factory was not a commercial success.
It was Josiah Spode (founder of the English Spode pottery) who between 1789 and 1791 improved the formula of this fine porcelain by tweaking the recipe and adding 50% bone ash and naming the clay ‘bone china’. This improved formula became a commercial success and the standard recipe for bone china which has been used ever since. Today sadly the biggest makers of bone china are found in China.
Adding bone to China clay and China stone made the porcelain whiter than any porcelain before. Also the bone ash gives the clay strength and translucency. If you hold a china plate up to light and can see the light through the plate, you know it’s bone china. Bone china is the only clay which gives this translucency quality.
The bone china clay that is used for flower making is the same receipe except it has gum arabic added to the clay to make it plyable. Gum arabic is made from the hardened sap of two species of acacia trees. Without gum arabic, bone china can only be used in slip casting, with gum arabic it can me used to make small flowers. But that is about all. You cannot sculpt or throw pots with bone china, it’s just for slip casting and flower making. I have managed to make larger objects like the rose candle holder in the image above, but that is after years of flower making and getting used to using this unique British clay.