Vitreous china

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Vitreous china
Material typeenamel
Physical properties
Density (ρ)1.83-2.48 g/cm3
Water absorption—over 24 hours<0.5%
Mechanical properties
Compressive strength (σc)400-800 kgf/cm2 (39226.6-78453.2 kPa)
Poisson's ratio (ν)0.5
Toilets are a common kind of vitreous china fixture Toilet fisher library.jpg
Toilets are a common kind of vitreous china fixture

Vitreous china is an enamel coating that is applied to ceramics, particularly porcelain, after they have been fired, though the name can also refer to the finished piece as a whole. The coating makes the porcelain tougher, denser, and shinier, and it is a common choice for things like toilets and sink basins. [1] [2] [3]

Contents

History

Vitreous china’s development tracks closely with other vitreous materials like glass, owing to the similar production process in terms of the materials needed, and preparing and firing such. Because an enamel is essentially glass applied to a substrate or surface to cover it, its production differs from that of glass by only a few steps.

The earliest known objects to be covered with a glaze are glazed stones made for jewellery, having been manufactured in Egypt as early as 4000 BC, in Mesopotamia from 5500-4000 BC, in Europe from 1400 BC and in the Indus Valley from 4500-3500 BC. [4] The first instance of applying an enamel to a substrate was in 3500 BP in Mycenae and Cyprus. [5] The champlevé technique, which involves first placing a glass enamel powder on a substrate and then firing it, was the predecessor technique for applying vitreous china and was used by the Celts from the 1st century BC. [5]

Uses

Vitreous china is used in a variety of household and sanitaryware items such as basins, toilets, bidets, urinals and bathtubs. [6] [ better source needed ] Items that use vitreous china are usually ones that are best when kept clean and sanitary, with which a coating of vitreous china enamel helps. Those same vitreous china items also benefit from having stains and spots removed easily due to the nature of their use.

Vitreous china can be occasionally found applied to kitchen countertops and related fixtures. [7] The low occurrence is due to vitreous china’s fragility when exposed to blunt force from crockery and other kitchen items. Instead, plastic and steel are examples of more common kitchen fixture materials.

Vitreous china can also be used for more aesthetic purposes. Items applied with a vitreous china enamel for this purpose include plates and other chinaware in china painting, and Fabergé eggs.

Structure

Vitreous china, like other enamels, is a glass-particulate composite, meaning it is glass (50-70 wt%) with non-silicate particles strewn about it that give it different properties. [8] Included in the vitreous enamel mixture is clay, which helps hold it all together and gives the necessary flexibility to form it into shape during firing, quartz which reduces shrinkage, and feldspar which increases the liquidity of the mixture when fired into its vitreous phase; this ensures low porosity in the final product. [9] [10]

After vitrification, vitreous china contains mullite, a crystal which forms as a result of reactions taking place in clay. [11] Not all of the quartz and feldspar liquify during firing, and so some of it remains as “relict” (its pre-firing powder form) in the final vitrified product. [11]

Physical properties

The general purpose of applying vitreous china enamel to a ceramic item like a washbasin is to provide protection for it, and it may be used secondarily for aesthetic purposes. In covering their porcelain substrate, vitreous china gives anti-corrosive properties and helps against weathering and heat. [5] Its non-porosity also prevents bacteria from entering the surface of ceramic material, and so keeps it from building up. Its porosity makes it absorb less than 0.5% of water. [12] The porosity of vitreous china can be reduced by increasing its feldspar content. [9]

Vitreous china is translucent, which, along with its protective nature, has made it preserve artefacts such as jewellery and potentially preserve them in the same state for thousands of years. [4]

Viscosity while vitreous china is in its liquid phase during firing depends on its constitutive ratio of glass to other particles- a higher quantity of particles results in higher viscosity. [11] Vitreous china’s density post vitrification ranges from 1.83 to 2.48 grams per cubic centimetre. [13] Its Poisson ratio is 0.5. [11] Its flexural strength is 400-800 kgf/cm2. [14]

Production

In most cases, vitreous china consists of a mix of clay, feldspar, flint and quartz sand. [11] This mix is usually fired once at 1200–1300 °C for most applications, and twice fired for use in crockery with a first firing at 900–950 °C and a second firing at 1200–1250 °C. Crockery is fired twice to reduce its porosity. [9] To make the mix more workable, water is usually added. The firing temperature chosen is important, as vitreous and ceramic bodies are less strong and more porous if under or over fired. [15]

Creep is the unwanted distortion a vitreous body undergoes during firing, and is influenced by the substance's rheological properties. [8] [11] Such properties depend on the particles in vitreous china's glass mixture, which can vary in type, size (1-50μm), distribution or shape. [11] The amount of mullite in vitreous china, which is determined by the amount of clay in the starting mixture, is the primary determinant for creep rate during firing. [16] [11]

Related Research Articles

<span class="mw-page-title-main">Ceramic</span> Inorganic, nonmetallic solid prepared by the action of heat

A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick.

<span class="mw-page-title-main">Pottery</span> Craft of making objects from clay

Pottery is the process and the products of forming vessels and other objects with clay and other raw materials, which are fired at high temperatures to give them a hard and durable form. The place where such wares are made by a potter is also called a pottery. The definition of pottery, used by the ASTM International, is "all fired ceramic wares that contain clay when formed, except technical, structural, and refractory products". End applications include tableware, decorative ware, sanitaryware, and in technology and industry such as electrical insulators and laboratory ware. In art history and archaeology, especially of ancient and prehistoric periods, pottery often means vessels only, and sculpted figurines of the same material are called terracottas.

<span class="mw-page-title-main">Porcelain</span> Ceramic material

Porcelain is a ceramic material made by heating raw materials, generally including kaolinite, in a kiln to temperatures between 1,200 and 1,400 °C. The greater strength and translucence of porcelain, relative to other types of pottery, arise mainly from vitrification and the formation of the mineral mullite within the body at these high temperatures. End applications include tableware, decorative ware such as figurines, and products in technology and industry such as electrical insulators and laboratory ware.

<span class="mw-page-title-main">Vitrification</span> Transformation of a substance into a glass

Vitrification is the full or partial transformation of a substance into a glass, that is to say, a non-crystalline amorphous solid. Glasses differ from liquids structurally and glasses possess a higher degree of connectivity with the same Hausdorff dimensionality of bonds as crystals: dimH = 3. In the production of ceramics, vitrification is responsible for their impermeability to water.

<span class="mw-page-title-main">Vitreous enamel</span> Material made by fusing powdered glass to a substrate by firing

Vitreous enamel, also called porcelain enamel, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C. The powder melts, flows, and then hardens to a smooth, durable vitreous coating. The word vitreous comes from the Latin vitreus, meaning "glassy".

<span class="mw-page-title-main">Earthenware</span> Nonvitreous pottery

Earthenware is glazed or unglazed nonvitreous pottery that has normally been fired below 1,200 °C (2,190 °F). Basic earthenware, often called terracotta, absorbs liquids such as water. However, earthenware can be made impervious to liquids by coating it with a ceramic glaze, and is used for the great majority of modern domestic earthenware. The main other important types of pottery are porcelain, bone china, and stoneware, all fired at high enough temperatures to vitrify. End applications include tableware, decorative ware such as figurines.

<span class="mw-page-title-main">Stoneware</span> Term for pottery or other ceramics fired at a relatively high temperature

Stoneware is a rather broad term for pottery fired at a relatively high temperature. A modern definition is a vitreous or semi-vitreous ceramic made primarily from stoneware clay or non-refractory fire clay. End applications include tableware, decorative ware such as vases.

<span class="mw-page-title-main">Islamic pottery</span>

Medieval Islamic pottery occupied a geographical position between Chinese ceramics, the unchallenged leaders of Eurasian production, and the pottery of the Byzantine Empire and Europe. For most of the period it can fairly be said to have been between the two in terms of aesthetic achievement and influence as well, borrowing from China and exporting to and influencing Byzantium and Europe. The use of drinking and eating vessels in gold and silver, the ideal in ancient Rome and Persia as well as medieval Christian societies, is prohibited by the Hadiths, with the result that pottery and glass were used for tableware by Muslim elites, as pottery also was in China but was much rarer in Europe and Byzantium. In the same way, Islamic restrictions greatly discouraged figurative wall-painting, encouraging the architectural use of schemes of decorative and often geometrically patterned titles, which are the most distinctive and original specialty of Islamic ceramics.

<span class="mw-page-title-main">Bone china</span> Porcelain composed of bone ash, feldspathic material, and kaolin

Bone china is a type of ceramic that is composed of 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 animal bone and calculated calcium phosphate. Bone china is the strongest of the porcelain or china ceramics, having very high mechanical and physical strength and chip resistance, and is known for its high levels of whiteness and translucency. Its high strength allows it to be produced in thinner cross-sections than other types of porcelain. Like stoneware, it is vitrified, but is translucent due to differing mineral properties.

<span class="mw-page-title-main">Slip casting</span> Technique for forming pottery

Slip casting, or slipcasting, is a ceramic forming technique, and is widely used for shapes that can not easily be formed by other techniques. The technique involves a clay body slip, usually prepared in a blunger, being poured into plaster moulds and allowed to form a layer, the cast, on the internal walls of the mould.

<span class="mw-page-title-main">Porcelain tile</span>

Porcelain tiles or ceramic tiles are porcelain or ceramic tiles commonly used to cover floors and walls, with a water absorption rate of less than 0.5 percent. The clay used to build porcelain tiles is generally denser. They can either be glazed or unglazed. Porcelain tiles are one type of vitrified tiles and are sometimes referred to as porcelain vitrified tiles.

<span class="mw-page-title-main">Ceramic glaze</span> Fused coating on ceramic objects

Ceramic glaze, or simply glaze, is a glassy coating on ceramics. It is used for decoration, to ensure the item is impermeable to liquids and to minimise the adherence of pollutants.

<span class="mw-page-title-main">Glaze defects</span> Flaws in a ceramic glaze

Glaze defects are any flaws in the surface quality of a ceramic glaze, its physical structure or its interaction with the body.

<span class="mw-page-title-main">Frit</span> Fused, quenched and granulated ceramic

A frit is a ceramic composition that has been fused, quenched, and granulated. Frits form an important part of the batches used in compounding enamels and ceramic glazes; the purpose of this pre-fusion is to render any soluble and/or toxic components insoluble by causing them to combine with silica and other added oxides. However, not all glass that is fused and quenched in water is frit, as this method of cooling down very hot glass is also widely used in glass manufacture.

This is a list of pottery and ceramic terms.

<span class="mw-page-title-main">Fritware</span>

Fritware, also known as stone-paste, is a type of pottery in which frit is added to clay to reduce its fusion temperature. The mixture may include quartz or other siliceous material. An organic compound such as gum or glue may be added for binding. The resulting mixture can be fired at a lower temperature than clay alone. A glaze is then applied on the surface.

The room-temperature form of quartz, α-quartz, undergoes a reversible change in crystal structure at 573 °C to form β-quartz. This phenomenon is called an inversion, and for the α to β quartz inversion is accompanied by a linear expansion of 0.45%. This inversion can lead to cracking of ceramic ware if cooling occurs too quickly through the inversion temperature. This is called dunting, and the resultant faults as dunts. To avoid such thermal shock faults, cooling rates not exceeding 50 °C/hour have been recommended.

<span class="mw-page-title-main">Conservation and restoration of ceramic objects</span>

Conservation and restoration of ceramic objects is a process dedicated to the preservation and protection of objects of historical and personal value made from ceramic. Typically, this activity of conservation-restoration is undertaken by a conservator-restorer, especially when dealing with an object of cultural heritage. Ceramics are created from a production of coatings of inorganic, nonmetallic materials using heating and cooling to create a glaze. These coatings are often permanent and sustainable for utilitarian and decorative purposes. The cleaning, handling, storage, and in general treatment of ceramics is consistent with that of glass because they are made of similar oxygen-rich components, such as silicates. In conservation ceramics are broken down into three groups: unfired clay, earthenware or terracotta, and stoneware and porcelain.

Industrial porcelain enamel is the use of porcelain enamel for industrial, rather than artistic, applications. Porcelain enamel, a thin layer of ceramic or glass applied to a substrate of metal, is used to protect surfaces from chemical attack and physical damage, modify the structural characteristics of the substrate, and improve the appearance of the product.

<span class="mw-page-title-main">Ceramic art</span> Decorative objects made from clay and other raw materials by the process of pottery

Ceramic art is art made from ceramic materials, including clay. It may take varied forms, including artistic pottery, including tableware, tiles, figurines and other sculpture. As one of the plastic arts, ceramic art is a visual art. While some ceramics are considered fine art, such as pottery or sculpture, most are considered to be decorative, industrial or applied art objects. Ceramic art can be created by one person or by a group, in a pottery or a ceramic factory with a group designing and manufacturing the artware.

References

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  2. ↑ Philippe Boch; Jean-Claude Nièpce (5 January 2010). Ceramic Materials: Processes, Properties, and Applications. John Wiley & Sons. p. 117. ISBN   978-0-470-39454-0 . Retrieved 25 September 2012.
  3. ↑ William L. Ventolo (1 May 1995). Your Home Inspection Guide. Dearborn Trade Publishing. p. 126. ISBN   978-0-7931-1336-1 . Retrieved 25 September 2012.
  4. 1 2 Angelini, I., Gratuze, B., & Artiolo, G. (2019). Glass and other vitreous materials through history. EMU notes in mineralogy, 20, 87-150.
  5. 1 2 3 Rossi, S., Russo, F., & Compagnoni, A. M. (2020). A brief history of porcelain enamel: from artistic enamel to technical enamelling . Scholarly community encyclopedia.
  6. ↑ Mani, Venkat. "What is Sanitary ware? Definition & Meaning". Ceramic Ninja. Retrieved 2020-05-03.
  7. ↑ Halepis, Harriette (20 January 2021). "What is Vitreous China?". InfoBloom. Retrieved 27 April 2021.{{cite web}}: CS1 maint: url-status (link)
  8. 1 2 Bergstrøm, Lennart (2017). "Rheology of Concentrated Suspensions". Surface and Colloid Chemistry in Advanced Ceramics Processing: 193–244. ISBN   9781351412674.
  9. 1 2 3 Bonnet, J.-P., & Gaillard, J.-M. (2007). Silicate Ceramics. In P. Boch, & J.-C. Niepce, Ceramic materials processes, properties and applications (pp. 117-118). London: ISTE.
  10. ↑ Cambier, Francis; Leriche, Anne (1996). "Vitrification". Materials Science and Technology—A Comprehensive Treatment. 17B: 123–144. doi:10.1002/9783527603978.mst0200. ISBN   9783527603978.
  11. 1 2 3 4 5 6 7 8 Porte, F. (2002). Creep of Vitreous China: Influence of Particle Size. Whitewares & materials a collection of papers presented at the 104th annual meeting of the American Ceramic Society and the Whitewares and Materials Division fall meeting, back to the basics, held in conjunction with the ACerS Southeastern Section and the (p. 177). St Louis, Missouri; Asheville, North Carolina: The American Ceramic Society.
  12. ↑ "Vitreous China – Sibelco" . Retrieved 2021-05-29.
  13. ↑ Parveen, Shahnaj; Jahan, Shirin Akter (2010). "Investigation on Physico-Chemical Properties of Vitreous China Sanitary Ware from Local Clays". Bangladesh Journal of Scientific and Industrial Research. 45 (4): 387–392. doi: 10.3329/bjsir.v45i4.7386 . ISSN   2224-7157.
  14. ↑ EP 0584977,Matsumoto, Akio&Nishikawa, Toshiya,"Vitreous china, method for preparing the vitreous china, and sanitary ware produced therefrom",published 1994-03-02, assigned to Toto Ltd.
  15. ↑ Sortwell, H (1923). "The Effect of Variation in Firing on the Physical Properties of Vitreous China Bodies1". Journal of the American Ceramic Society. 6 (8): 915–936. doi:10.1111/j.1151-2916.1923.tb17759.x.
  16. ↑ Rhanim, H.; Olagnon, C.; Fantozzi, G.; Torrecillas, R. (1997-01-01). "Experimental characterisation of high temperature creep resistance of mullite". Ceramics International. 23 (6): 497–507. doi:10.1016/S0272-8842(96)00061-2. ISSN   0272-8842.
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