Se denomina arcilla de bola a una arcilla sedimentaria, de la familia de las caolinitas, la composición oscila entre 20-80% de caolinita, 10-25% mica, 6-65% cuarzo. Se trata de arcillas en estado natural de color gris, por el alto contenido de materia orgánica, tras su cocción pasa a ser blanco. Sus características principales es su grano muy fino, excelente plasticidad y alta resistencia en fresco, aunque es difícil usarla sola, ya que tiene una alta contracción (casi un 20%).
Tiene mucha plasticidad y poco calcio, se extraía manualmente, a finales del siglo XIX, de los campos del sur de Inglaterra.
Localized seams in the same deposit have variations in composition, including the quantity of the major minerals, accessory minerals and carbonaceous materials such as lignite.[1] They are fine-grained and plastic in nature.
Ball clays are relatively scarce deposits due to the combination of geological factors needed for their formation and preservation. They are mined in parts of the Eastern United States and from three sites[2] in Devon and Dorset in South West England.[3] They are commonly used in the construction of many ceramic articles, where their primary role is to either to impart plasticity or to aid rheological stability during the shaping processes.
Historia[]
Su nombre procede de las bolas que hacían los mineros para facilitar su extracción y transporte.
El uso de esta arcilla en Britain data de la era romana.
The name "ball clay" is believed to derive from the time when the clay was mined by hand. It was cut into 15 to 17-kilogram cubes and during transport the corners of the cubes became rounded off leaving "balls".[1]
The ceramic use of ball clays in Britain dates back to at least the Roman era. More recent trade began when a clay was needed to construct tobacco pipes in the 16th and 17th century.[4] In 1771 Josiah Wedgwood signed a contract for 1400 tons a year of ball clay with Thomas Hyde of Purbeck enabling him to fire thinner walled ceramics.[5]
Aplicaciones en cerámica[]
- Se usa en las pastas, en distintas proporciones, dependiendo de la temperatura de quema del resultado.
- aumenta la plasticidad de las pastas en general, agregada en un 10-20% como plastificante a una pasta ya formada.
PM: 374.79
55.90 % | SiO2 |
27.20 % | Al2O3 |
1.10 % | K2O |
0.20 % | Na2O |
0.40 % | MgO |
0.40 % | CaO |
1.10 % | Fe2O3 |
1.20 % | TiO2 |
12.50 % | L.O.I. |
- Fuente:Matrix
Véase[]
- Ball clay
- Ball clay and the Stover Canal
Referencias[]
- ↑ 1,0 1,1 What is ball clay?. Industrial Minerals Association - North America. Retrieved on 2008-08-05.
- ↑ The Bovey Basin in South Devon, the Petrockstowe Basin in North Devon and the Wareham Basin in South Dorset.
- ↑ Highley, David; Bloodworth, Andrew; Bate, Richard (2006). Ball Clay - Mineral Planning Factsheet (pdf file). British Geological Survey. Retrieved on 2008-08-05.
- ↑ The Widespread Use of Ball Clay. Introduction to Ball Clays. The Ball Clay Heritage Society. Retrieved on 2008-08-05.
- ↑ History of Ball Clay - Swanage Railway. The Purbeck Mineral & Mining Museum. Retrieved on 2008-08-05.
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