Sourcing and Delivery of Materials
The story of the mill usually starts with explaining about the processes when the material has been delivered to the site. Of course they had to be sourced. Flints came from the beaches of the east and south coasts of England and near continent. The image shows women gathering stones from the beach at Dieppe, France in the early 1900s. The stones were sorted and flints could easily be transported to Etruria by coastal shipping and canal. Bone, usually from cattle, came from the slaughterhouses. Originally it would be sourced locally but as demand grew it came from all parts of the UK and overseas. The first process with bone was to boil it, a very smelly process, with the by product being animal glue and size. The clean bones could then be calcined. For manufacturing bone china only the shin bone and knuckle could be used.
Calcining
The kiln seen today was used to calcine (roast) flints. In their natural state they are hard and black but when heated to above 1000o centigrade crystalline water is driven off to leave a softer, lighter, white product suitable for grinding to a fine powder. The calcining kiln consists of two chambers, see images below, with a hovel built above them to create a draught to aid combustion. Filling the kiln was a very skilled job. Flints would be built up in layers with slack (small pieces) coal using approximately 1 hundredweight (51Kg) of coal per 1 ton (1.02 tonnes) of flint. It would be allowed to combust for 8 to 16 hours depending on the fuel and climatic conditions and then left to cool before being removed through draw holes at the bottom into the crusher room next door. Production of ground flint ceased in the 1930s. Bone was treated in a similar way after first being boiled to remove tissue, this produced glue, a saleable by-product. Wood was used as the fuel because bone is more combustible and is prone to contamination from the iron pyrites in coal. Calcined bone is softer and whiter than in its natural state and suitable for grinding. After removal from the kiln the material would be washed to remove remaining ash before either crushing or moving directly into the pan room for grinding.
