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Bone ash is a white material produced by the calcination of bones. Typical bone ash consists of about 55.82% calcium oxide , 42.39% phosphorus pentoxide , and 1.79% water . [ 1 ] The exact composition of these compounds varies depending upon the type of bones being used, but generally the formula for bone ash is Ca 5 (OH)(PO 4 ) 3 .
Bone china is a type of vitreous, translucent pottery, [1] the raw materials for which include bone ash, feldspathic material and kaolin. It has been defined as "ware with a translucent body" containing a minimum of 30% of phosphate derived from calcined animal bone or calcium phosphate. [ 2 ]
Bone char (Latin: carbo animalis) is a porous, black, granular material produced by charring animal bones. Its composition varies depending on how it is made; however, it consists mainly of tricalcium phosphate (or hydroxyapatite ) 57–80%, calcium carbonate 6–10% and carbon 7–10%. [ 1 ]
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Early ceramics were porous, absorbing water easily. It became useful for more items with the discovery of glazing techniques, which involved coating pottery with silicon, bone ash, or other materials that could melt and reform into a glassy surface, making a vessel less pervious to water.
Josiah Spode was born in Lane Delph, Fenton, Staffordshire.Spode was a pauper's son and also a pauper's orphan at the age of six. In 1745 his elder sister Ann married Ambrose Gallimore, [1] who in 1754 obtained the lease of the Caughley porcelain factory near Broseley.
The earliest Bow porcelains are of soft-paste incorporating bone ash, forming a phosphatic body that was a precursor of bone china. By 1749–1750 the business had moved from Bow to 'New Canton', a new factory on the Essex side of the River Lea, close to Bow Bridge, just west of Stratford High Street and beside Bow Back River.
Ink and wash drawings are also prevalent in the period. In addition, these other drawing techniques required less effort and were more forgiving than silver, which resists erasure and leaves a fainter line. Furthermore, the preparation of silverpoint supports, usually with hide glue with finely ground bone ash, was labor-intensive.