Slip casting

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Porcelain figurine which had been formed by slipcasting Lovers, unidentified, porcelain - Musei Capitolini - Rome, Italy - DSC05956.jpg
Porcelain figurine which had been formed by slipcasting
Slipcasting allows the shaping of complex shapes, such as this toilet bowl Flush toilet bowl 1.jpg
Slipcasting allows the shaping of complex shapes, such as this toilet bowl
Pouring casting slip into a mould Slip Casting di kilang Claytan.png
Pouring casting slip into a mould
Removing the last parts of a mould from a slipcast vase Sevres - petit coulage - demoulage 21.jpg
Removing the last parts of a mould from a slipcast vase

Slip casting, or slipcasting, is a ceramic forming technique, and is widely used in industry and by craft potters to make ceramic forms. This technique is typically used to form complicated shapes like figurative ceramics that would be difficult to be reproduced by hand or other forming techniques. [1] 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.

Contents

It is suited for the consistent and precise shaping of complex shapes. [2] [3] It is the standard shaping technique for sanitaryware, such as toilets and basins, and is commonly used for smaller pieces like figurines and teapots. [4] [5] [6]

History

The technique was first developed in China during the Tang dynasty (618–917), but was relatively little-used in China until recent times[ when? ]. [7] It seems to have been reinvented independently in England around 1745 "reputedly by Ralph Daniels of Corbridge", [8] and before long was widely used by European porcelain manufacturers, and then became the main forming technique for sanitaryware by the end of the century.

Technical considerations

Solid casting is used to produce solid articles, such as cup handles; for this the mold frequently includes a reservoir of excess slip. Hollow casting is used to produce articles such as teapots. [9]

The properties of a casting slip depends on multiple factors, including: [10]

Additionally, factors affecting the rate of formation of the cast piece include: [11]

Schematic of the formation of a cast piece Slip casting principle.png
Schematic of the formation of a cast piece

The casting slip is poured into a porous mould. Due to capillary pressure from the mold, a semi-solid particulate layer is formed on the mould through deposition of the solids in the slip. After a period of time, determined in advance by testing, the cast piece is removed from the mold; the cast needs to be sufficiently firm to handle without damage. The cast piece may then be fettled to remove the mold seam, before being dried to remove the remaining water. This typically results in a greenware piece which is then ready for subsequent processing, including glazing and firing. [12] [4]


Part of a mould for a teapot Gladstone mould making tea pot 3839.JPG
Part of a mould for a teapot
Half a mould showing half of a solid cast piece Sevres - grand coulage 11.jpg
Half a mould showing half of a solid cast piece

Casting times

A lavatory closet typically takes around 40 to 60 minutes to cast using the conventional technique, [13] [14] with a Swiss manufacturer noting that "preparing the mould and casting a single piece can take up to 40 minutes." [15] Thinner sections will be quicker, with one source advising 5–10 mm taking 10–15 minutes. [16]

Casting times for ceramic tableware have been reported as 35 to 60 minutes for earthenware and 8 to 20 minutes for bone china. [17] Other reports include: 30–50 minutes at a US studio pottery; around 60 minutes at a small Portuguese manufacturer of decorative ceramics; "approximately 15 minutes" from a US distance learning university; 15–20 minutes in an article for studio potters; and 15–45 minutes in a guide for beginners. [18] [19] [20] [21] [22]

Casting times are notably shorter by pressure casting, with 2 minutes reported for tableware bowls and dishes, and 6–8 minutes for sanitaryware. [23] The cycle time per piece of sanitaryware using high pressure at Duravit is reported to be 20 minutes. [24]

Solids content of the slip

To achieve an acceptable rate of cast formation and minimize drying shrinkage, a slip with a high content of solids is needed. The generally-accepted solids content of a Vitreous China sanitaryware casting slip ranges between 72 and 75% by weight, which corresponds to slip densities of 1.80–1.85 g/cm3. [25]

Certain chemicals, known as deflocculants, are used to disperse agglomerates in the slip, and so decrease the viscosity and also allow a higher solids content; the latter is important to minimize drying shrinkage. Examples of deflocculants include sodium carbonate and sodium silicate. [26] [27] [28] Typical deflocculant additions used for a Vitreous China casting slip are 0.1-0.65%; the rheological properties of the clay components are the main influencing factors for the dosage. [29]

A mathematical formula developed by Alexandre Brongniart of Sèvres Porcelain is used to determine the dry material content of the slip. This has become to be known as Brongniart's formula. [28]

Pressure casting

Pressure casting is a development of traditional slipcasting which was developed in the 1970s for the production of sanitaryware and more recently has been applied to tableware. [30] [31]

Specially-developed polymeric materials allow a mold to be subject to application of external pressures up to 4.0 MPa; much higher than slip casting in plaster molds where the capillary forces correspond to a pressure of around 0.1–0.2 MPa. [32] The high pressure leads to much faster casting rates and, hence, faster production cycles: one study found that by increasing the pressure from 0.25 to 4.0 bar (3.6 to 58 psi) decreased the casting time for a 6-mm cast of a porcelain body from about 45 to 15 min. [33] Using pressure casting, a Geberit factory in Finland casts a toilet in 20 minutes. [34]

Furthermore, the application of high-pressure air through the polymeric molds upon demolding the cast means that a new casting cycle can be started immediately in the same mold, unlike plaster moulds which require lengthy drying times. The polymeric materials have much greater durability than plaster and, therefore, it is possible to achieve products with better dimensional tolerances and much longer mold life. [10] [35]

Advantages of pressure casting over conventional casting have been summarized as higher productivity, higher yield, improved ware quality, lower distortion of the cast piece, reduced surface defects, reduced production space, reduced demand for molds, reduced energy costs, and readily fitting with the automation of demolding and handling. [36]

Ceramic laminates

As a processing technique for ceramic laminates, a ceramic powder is often placed in suspension to form a slip with a high solids content (>60 wt%) as well as a very low viscosity value (<40 mPa). A series of layers can be formed by changing the composition of the slips used in repeated castings. If the chemistry of the materials being used is well understood, the thickness of the layers can be controlled by varying the length of time involved in the casting. [37]

Slipware

Slip-cast ware, objects that are formed using slip casting, should not be confused with slipware, pottery that is formed by any technique and then decorated using slip. [38] The French for slip is barbotine (coulée en barbotine means slip casting). As far back as the Roman empire, potters created what is termed "Barbotine ware" by using clay slip to decorate the surface of pots. [39] "Barbotine pottery" is sometimes used for 19th-century French and American pottery with added slip cast decoration, [40] as well as (confusingly) 17th century English slipware that is decorated with thick blobs of slip. [41]

Related Research Articles

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, sanitary ware, 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 only vessels, and sculpted figurines of the same material are called terracottas.

<span class="mw-page-title-main">Terracotta</span> Clay-based earthenware used for sculpture

Terracotta, also known as terra cotta or terra-cotta, is a clay-based non-vitreous ceramic fired at relatively low temperatures. It is therefore a term used for earthenware objects of certain types, as set out below.

<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 such a process 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 and decorative ware such as figurines.

<span class="mw-page-title-main">Lost-wax casting</span> Process by which a duplicate metal sculpture is cast from an original sculpture

Lost-wax casting – also called investment casting, precision casting, or cire perdue – is the process by which a duplicate sculpture is cast from an original sculpture. Intricate works can be achieved by this method.

This page describe terms and jargon related to sculpture and sculpting.

<span class="mw-page-title-main">Slipware</span> Pottery with a coating of slip

Slipware is pottery identified by its primary decorating process where slip is placed onto the leather-hard (semi-hardened) clay body surface before firing by dipping, painting or splashing. Slip is an aqueous suspension of a clay body, which is a mixture of clays and other minerals such as quartz, feldspar and mica. The slip placed onto a wet or leather-hard clay body surface by a variety of techniques including dipping, painting, piping or splashing. Slipware is the pottery on which slip has been applied either for glazing or decoration. Slip is liquified clay or clay slurry, with no fixed ratio of water and clay, which is used either for joining pottery pieces together by slip casting with mould, glazing or decorating the pottery by painting or dipping the pottery with slip.

Ceramic forming techniques are ways of forming ceramics, which are used to make everything from tableware such as teapots to engineering ceramics such as computer parts. Pottery techniques include the potter's wheel, slip casting and many others.

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

Barbotine is the French for ceramic slip, or a mixture of clay and water used for moulding or decorating pottery. In English the term is used for three different techniques of decorating pottery, though in all cases mainly for historical works. For clarity, these types are numbered here as A-C.

<span class="mw-page-title-main">Investment casting</span> Industrial process based on lost-wax casting

Investment casting is an industrial process based on lost-wax casting, one of the oldest known metal-forming techniques. The term "lost-wax casting" can also refer to modern investment casting processes.

<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">Pattern (casting)</span>

In casting, a pattern is a replica of the object to be cast, used to form the sand mould cavity into which molten metal is poured during the casting process. Once the pattern has been used to form the sand mould cavity, the pattern is then removed, molten metal is then poured into the sand mould cavity to produce the casting. The pattern is non consumable and can be reused to produce further sand moulds almost indefinitely.

<span class="mw-page-title-main">Slip (ceramics)</span> Slurry of clay and water

A slip is a clay slurry used to produce pottery and other ceramic wares. Liquified clay, in which there is no fixed ratio of water and clay, is called slip or clay slurry which is used either for joining leather-hard (semi-hardened) clay body together by slipcasting with mould, glazing or decorating the pottery by painting or dipping the pottery with slip. Pottery on which slip has been applied either for glazing or decoration is called slipware.

This is a list of pottery and ceramic terms.

<span class="mw-page-title-main">Ancient Roman pottery</span> Produced within the Roman Republic and Roman Empire

Pottery was produced in enormous quantities in ancient Rome, mostly for utilitarian purposes. It is found all over the former Roman Empire and beyond. Monte Testaccio is a huge waste mound in Rome made almost entirely of broken amphorae used for transporting and storing liquids and other products – in this case probably mostly Spanish olive oil, which was landed nearby, and was the main fuel for lighting, as well as its use in the kitchen and washing in the baths.

<span class="mw-page-title-main">Casting</span> Manufacturing process in which a liquid is poured into a mold to solidify

Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting materials are usually metals or various time setting materials that cure after mixing two or more components together; examples are epoxy, concrete, plaster and clay. Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods. Heavy equipment like machine tool beds, ships' propellers, etc. can be cast easily in the required size, rather than fabricating by joining several small pieces. Casting is a 7,000-year-old process. The oldest surviving casting is a copper frog from 3200 BC.

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

Ceramics in Mexico date back thousands of years before the Pre-Columbian period, when ceramic arts and pottery crafts developed with the first advanced civilizations and cultures of Mesoamerica. With one exception, pre-Hispanic wares were not glazed, but rather burnished and painted with colored fine clay slips. The potter's wheel was unknown as well; pieces were shaped by molding, coiling and other methods.

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

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.

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

A potbank is a colloquial name for a pottery factory in North Staffordshire used to make bone china, earthenware and sanitaryware.

<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

  1. ↑ Morgenthal, Deborah; Tourtillott, Suzanne J. E., eds. (2008). The Penland Book of Ceramics: Master Classes in Ceramic Techniques. New York: Lark Books; Sterling Publishing Company, Inc. p. 72. ISBN   978-1-60059-275-1 . Retrieved 16 October 2021.
  2. ↑ Rijke, Jenny (March 4, 2020). "Slip Casting Molds: What are they, why use them and how to achieve different aesthetics". Jenny RIjke. Archived from the original on 16 October 2021. Retrieved 16 October 2021.
  3. ↑ Toma, McKenzie (August 29, 2018). "What Even Is Slipcasting?". East Fork. Retrieved 16 October 2021.
  4. 1 2 Osborne, Harold (1975). The Oxford companion to the decorative arts. Oxford: Clarendon Press. p. 746. ISBN   0198661134.
  5. ↑ Bhargava, A. K. (2012). Engineering Materials : polymers, ceramics and composites (Second ed.). New Delhi: PHI Learning Pvt. Ltd. p. 196. ISBN   9788120346215 . Retrieved 16 October 2021.
  6. ↑ "Casting Your Miniature Doll Molds". Cynthis Howe Miniatures. Retrieved 16 October 2021.
  7. ↑ David W. Richerson, American Ceramic Society, The Magic of Ceramics, p. 41, 2012, Wiley, ISBN 9780470638057, google books
  8. ↑ Savage, George, and Newman, Harold, An Illustrated Dictionary of Ceramics, p. 265, 1985, Thames & Hudson, ISBN 0500273804
  9. ↑ 'Whitewares: Production, Testing And Quality Control.' W. Ryan, C. Radford. Pergamon Press, 1987.
  10. 1 2 'Sanitaryware Technology'. Domenico Fortuna. Gruppo Editoriale Faenza Editrice S.p.A. 2000.
  11. ↑ "Reference Guide To Making and Adjusting Casting Slip". The Ceramic Shop. Retrieved 16 October 2021.
  12. ↑ Whitewares: Production, Testing And Quality Control.' W. Ryan, C. Radford. Pergamon Press, 1987.
  13. ↑ 'Materials And Equipment – Whitewares. Volume 13, Issue 1/2. J. B. Wachtman. Wiley & Sons. Pg. 402
  14. ↑ 'Effect Of The Physical Properties Of Slip On The Molding Of Commercial Grade Sanitary Ware' V.V. Mikhalev, V.V. Serov, A.S. Glass and Ceramics, 64(3-4), 129–131, 2007. Pg. 131
  15. ↑ "125 years | Design & Innovation".
  16. ↑ with a https://www.laufen.com/news-stories/earth-water-fire_laufen
  17. ↑ ’The Control Of Casting Slip: A Survey Of Current Casting Practice In The Tableware Industry’ RP.749. Ceram Research, 1987
  18. ↑ "You Will be Slip Casting Ceramics with These 5 Easy Steps". 9 October 2019.
  19. ↑ "All you need to know about Slip Casting of Ceramics (We do it everyday!)". 7 November 2019.
  20. ↑ "A Simple Step-by-Step Guide to Slip Casting". 13 April 2015.
  21. ↑ 'In The Studio: Mixing Casting Slip: Tips and Tricks' D. S. Smith. Pottery Making Illustrated. Nov/Dec 2020
  22. ↑ ‘Ceramics: A Beginner’s Guide To Tools And Techniques’ E. Landberger, M. Lundin. Allworth Press, 2012
  23. ↑ ’A Comparison Of Plaster Casting And Pressure Casting Of Sanitaryware With Particular Reference To Clay Properties’ C. Hogg. Ceramics International. Volume 11, Issue 1, 1985, Pg. 32
  24. ↑ "Duravit makes new investments in high-pressure casting". 13 February 2017.
  25. ↑ 'Ceramics, Glass and Glass-Ceramics – From Early Manufacturing Steps Towards Modern Frontiers' F. Baino, M. Tomalino, D. Tulyaganov. Springer International Publishing, 2021
  26. ↑ Gadow, Rainer; Kern, Frank (1 January 2014). "2.06 - Advanced Manufacturing of Hard Ceramics". Comprehensive Hard Materials. Amsterdam: Elsevier. pp. 207–230. doi:10.1016/B978-0-08-096527-7.00025-8. ISBN   978-0-08-096528-4.
  27. ↑ Wandless, Paul Andrew. "How to Make Casting Slip from Your Clay Body - A Simple Technique". Ceramic Arts Network Daily. Retrieved 16 October 2021.
  28. 1 2 Singer, Felix; Singer, Sonja S. (1971). Industrial Ceramics. London: Chapman & Hall. ISBN   9788120401624.
  29. ↑ 'Ceramics, Glass and Glass-Ceramics - From Early Manufacturing Steps Towards Modern Frontiers' F. Baino, M. Tomalino, D. Tulyaganov. Springer International Publishing, 2021
  30. ↑ "Ceramicindustry.com". Ceramic industries.com. 2000-11-21. Archived from the original on 2011-07-08. Retrieved 2010-09-04.
  31. ↑ Dictionary Of Ceramics. Arthur Dodd & David Murfin. 3rd edition. The Institute Of Minerals. 1994.
  32. ↑ 'Microstructure-Performance Relation in PMMA-Based Open-Cell Porous Materials for High Pressure Ceramic Sanitaryware Casting. Y. Ergün, C. Dirier, M. Yılmaz, C. Tokman, M. Tanoğlu. Key Engineering Materials. Trans Tech Publications, Ltd., May 2004
  33. ↑ 'Modern Ceramic Engineering' 3rd. edition. D.W.Richerson. CRC Press. 2005. Pg. 436
  34. ↑ "High-pressure ceramic production".
  35. ↑ "DGM-E.pdf" (PDF). Retrieved 2010-09-04.[ permanent dead link ]
  36. ↑ ’Clays For Pressure Casting Sanitaryware’ Brian Waters. Ceramic Forum International. Cfi/Ber. 89 (2012) No.1. Pg. E19
  37. ↑ Chan, Helen M. (August 1997). "LAYERED CERAMICS: Processing and Mechanical Behavior". Annual Review of Materials Science. 27 (1): 249–282. Bibcode:1997AnRMS..27..249C. doi:10.1146/annurev.matsci.27.1.249. ISSN   0084-6600 . Retrieved 15 October 2021.
  38. ↑ Hamer, Frank; Hamer, Janet (23 June 2004). The Potter's Dictionary of Materials and Techniques. Philadelphia: University of Pennsylvania Press. pp. 333–334. ISBN   978-0-8122-3810-5 . Retrieved 16 October 2021.
  39. ↑ Cooper, Emmanuel (2000). Ten Thousand Years of Pottery. Philadelphia: University of Pennsylvania Press. p. 52. ISBN   978-0-8122-3554-8 . Retrieved 16 October 2021.
  40. ↑ Frelinghuysen, Alice Cooney; Eidelberg, Martin; Spinozzi, Adrienne (25 September 2018). American Art Pottery: The Robert A. Ellison Jr. Collection. New York: Metropolitan Museum of Art. p. 43. ISBN   978-1-58839-596-2.
  41. ↑ "Pottery - 17th-century slipware". Encyclopedia Britannica.
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