True bone china is a special type of translucent porcelain. Instead of feldspar, bone ash is used as the flux. The process requires more careful attention than normal porcelain. The vitrification range is narrow, kilns need to be fired carefully. Ware often warps so badly that it must be fired without glaze and supported in setters during the firing (it is then glazed and fired again at a low temperature). Forming methods have to be adapted to the very low plasticity of the bodies. Glazes have to be adapted because the ware has zero porosity. The whole process is quite foreign to what workers in an average pottery would be accustomed to.
Now that is a translucent porcelain!
These are two cone 6 transparent glazed porcelain mugs with a light bulb inside. On the left is the porcelainous Plainsman M370 (Laguna B-Mix 6 would have similar opacity). Right is a zero-porosity New Zealand kaolin based porcelain called Polar Ice (from Plainsmanclays.com also)! The secret to making a plastic porcelain this white and translucent is not just the NZ kaolin, but the use of a very expensive plasticizer, VeeGum T, to enable maximizing the feldspar to get the fired maturity.
Out Bound Links
In Bound Links