China, bone

Bone china, which has a characteristic translucent appearance, consists of crystalline anorthite, CaO AI2O3 2Si02 and P-Ca3(P04)2, embedded in various glassy phases. The best quality bone china is produced in England, using ox-bone ash. A suitably fabricated mix of the composition below is fired at 1200-1240°C. It is then dipped in a suspension of glaze materials and fired at 1070-1100°C  

Bone ash has a variable composition which sometimes includes up to 10% CaC03, about 1% Si02 and traces of some metals. An average grade has the approximate composition indicated, which leads to bone china products with average oxide contents  

Hydroxyapatite may also be used, since it is converted to tricalcium phosphate on heating, but ox bone is to be preferred. This is because the latter has a lower content of trace metal impurities which are otherwise liable to slightly discolour the bone china product. 

One phosphate-containing enamel for ceramic materials can be formulated as follows  

Low-melting-point vitreous enamels for aluminium utilise as much as 30-40% P2O5 in their formulations [67]. The formation of protective films on metal surfaces (Section 12.7) in some cases involves the formation, in part, of glassy phosphate phases. These can be for corrosion protection or electrical insulation [68]. 

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J. T. Meckstroth 22 showed that the largest use for phosphoric acid is in sugar defecation. It is also used in the manufacture of jellies, preserves, and soft drinks in pharmaceutical preparations and in the rust-proofing of iron. The chief phosphates in industry are the calcium hydrophosphates used in making baking-powder, and self-rising flour sodium phosphates used in making boiler compounds, in laundry work, etc. The superphosphates are used in fertilizers. Calcium orthophosphate is the form of bone ash extensively used in the manufacture of bone china. 

Melamine resins found a wider range of uses, including tableware (cups, saucers, plates), and in decorative and industrial laminates. One might think that melamine tableware never was likely to rival bone china in delicacy and appeal but it was attractive enough for the canteen, kitchen, or nursery, and less fragile even than delft or unglazed earthenware. The mouldings were available in a variety of opaque and translucent colours, and for a time enjoyed considerable popularity. 

Bone china is a high quality product, whose ingredient mixture contains phosphate (40 to 50% bone ash). Used for crockery and ornamental objects... 

Heated and crushed animal bones were used copiously in making bone China, predominately in Britain, commencing around the mid-eighteenth century (Heimann, 2012 Heimann and Maggetti, 2014). As it turned out, by the end of the eighteenth century much research had been performed on calcium phosphates, which involved the names of many renowned scientists of the time... 

Bone china has a composition similar to that of porcelain, but at least 50 percent of the material is finely powdered bone ash. Like porcelain, bone china is strong and can be formed into dishes with very thin, translucent walls. Stoneware is a dense, hard, gray or tan ceramic that is less expensive than bone china and porcelain, but it is not as strong. As a result, stoneware dishes are usually thicker and heavier than bone china or porcelain dishes. 

Strictly speaking, bone ash functions mainly as a filler in bone china bodies and only acts as a flux to a limited extent. It is prepared by treating cattle bone with steam to remove fat and is then calcined at 800°-1000 C. The product is then wet-ground to... 

In the firing of bone china, which contains some 50% of bone ash, together with 25% each of china clay and stone, part of the calcium reacts with the whole of the metakaolin, Al2Si207, to form anorthite, CaAl2Si20g the remainder of the calcium forms tricalcium phosphate, Ca3(P04)2, whilst the excess phosphate reacts with the fluxes to form a complex glass. 

First, a solid model of the object has to be made. This would originally have been done in solid clay or with a pre-existing form. Nowadays it would generally be made of plastercine or Acrylic. These models are always oversized as the finished article shrinks both in the mould and in the kiln. Earthenware, bone china and porcelain may shrink by as much as 15 to 20 percent Parian is considerably more prone to shrinkage and may lose as much as 25 per cent. 

Around 1750, porcelain was produced with bone ash in England and given the name bone china ... 

Bone china Ornamental ceramics, ceramic tableware... 

Bone China has a similar recipe to hard-paste porcelain, but with the addition of 50% animal bone ash (calcium phosphate). This formulation improves strength, translucency, and whiteness of the product and was perfected by Josiah Spode at the end of the eighteenth century. It was then known as English China or Spode China. ... 

We stated at the beginning that this chapter is the pottery chapter. We will now summarize areas in which many of the techniques described above have been used, in some cases for milleimia, in pottery then we can do the same for glass. Classical porcelain can be as thin as a sheet of paper (<0.2 mm). Bone china, so called because even today it is made by adding -50% bone ash to a conventional hard-porcelain clay mixture, can be so thin that it is translucent. This ingredient is so critical that the UK imports bone ash from Argentina. 

Spode, Josiah (1733-1797) founded his pottery in 1770 at Stoke. He developed the formula for bone china that is still used. 

Tricalcium phosphate or hydroxyapatite is essential for making bone china, and artificial bone can be prepared by combining apatite with other materials (Chapter 12.10). 

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