Vitreous china

Vitreous china
Toilets are typically made of vitreous china
Material typeceramic
Physical properties
Density (ρ)1.83-2.48 g/cm3[1]
Water absorption—over 24 hours<0.5%[2]
Mechanical properties
Compressive strength (σc)400-800 kgf/cm2 (39226.6-78453.2 kPa)[3]
Poisson's ratio (ν)0.5[4]

Vitreous china is a dense, nonporous ceramic that is commonly used to make sanitary fixtures like toilets and sinks and robust crockery for use in environments like hospitals, where sanitation and durability are important.[5][6][7] The vitreous china material is typically coated with a porcelain enamel to produce a smooth, durable surface finish.

Structure

Vitreous china is made from clay with a higher than normal amount of feldspar.[6] The latter melts during firing and fills voids in the ceramic, reducing porosity.

After vitrification, vitreous china contains mullite, a crystal which forms as a result of reactions taking place in clay.[4] Not all quartz and feldspar liquify during firing, so some remain as "relict" in the final vitrified product.[4]

Physical properties

The low porosity of vitreous china means its water absorption is less than 0.5%.[2] The porosity of vitreous china can be reduced by increasing its feldspar content.[8]

While vitreous china is in its liquid phase during firing its viscosity depends on its constitutive ratio of glass to other particles—a higher quantity of particles results in higher viscosity.[4] Vitreous china's density post vitrification ranges from 1.83 to 2.48 grams per cubic centimetre.[1] Its Poisson ratio is 0.5.[4] Its flexural strength is 400–800 kgf/cm2.[3]

Production

In most cases, vitreous china consists of a mix of clay, feldspar, flint and quartz sand.[4] 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.[8] 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.[9]

Creep is the unwanted distortion a vitreous body undergoes during firing and is influenced by the substance's rheological properties.[4][10] Such properties depend on the particles in vitreous china's glass mixture, which can vary in type, size (1–50 μm), distribution or shape.[4] 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.[11][4]

References

  1. 1 2 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.
  2. 1 2 "Vitreous China – Sibelco". Retrieved 2021-05-29.
  3. 1 2 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.
  4. 1 2 3 4 5 6 7 8 9 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.
  5. ↑ Active Interest Media, Inc. (April 1977). Old-House Journal. Active Interest Media, Inc. p. 39. ISSN 0094-0178. Retrieved 25 September 2012.
  6. 1 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.
  7. ↑ 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.
  8. 1 2 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.
  9. ↑ Sortwell, H (1923). "The Effect of Variation in Firing on the Physical Properties of Vitreous China Bodies". Journal of the American Ceramic Society. 6 (8): 915–936. doi:10.1111/j.1151-2916.1923.tb17759.x.
  10. ↑ Bergstrøm, Lennart (2017). "Rheology of Concentrated Suspensions". Surface and Colloid Chemistry in Advanced Ceramics Processing: 193–244. ISBN 9781351412674.{{cite journal}}: CS1 maint: periodical has ISBN (link)
  11. ↑ 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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