In the United Kingdom china clay deposits that were found to be of a finer quality than elsewhere in Europe were discovered in Cornwall in the middle of the 18th century; their exploitation created the United Kingdom’s china clay industry. Its development in the 19th century was economically most important to Cornwall, since its growth took place at a time when the industry upon which Cornwall had previously depended for employment and wealth creation, tin mining, was being forced into decline by foreign competition. Changes in the papermaking industry and its expansion in the second half of the 19th century created a new and growing market for china clay.

The processes of extracting, refining, and drying china clay remain in essence the same as they were in the 19th century, although the application of technology has transferred to machines much of the work done by manual labor in the early days, improved the purity of the final product, and made it possible to extract other minerals that formerly went to waste. Even so, waste remains a formidable problem for the group; despite the use of sand and the application of much research, the production of one ton of clay still creates seven tons of waste. The first process is the pit operation, which involves exposing china clay deposits by removing the overburden. Some deposits may be as close to the surface as three feet while others may be hundreds of feet below ground. Hydraulic mining, by firing water jets from a cannon at the clay deposits, frees the deposits and creates a slurry which also contains sand and mica. The slurry is then pumped out and the coarser sand removed before the refining process takes place. This process takes out unwanted minerals such as quartz, mica, and feldspar. Geologically, china clay is formed in granite rocks by the decomposition of feldspar. At this stage chemical bleaching to remove the stains in the clay caused by mineral salts, particularly iron oxide, can add value to the final product, a technological advance not available until after World War II. ECC operates six refining plants in Devon and Cornwall that take clay from a number of pits and mix it in the quantities required for finished products of varying characteristics. The final drying process, which today usually takes place in natural gas-fired driers, was originally done in coal-fired kilns and even, at some pits, wind and sun dried.

ECC Group