ARCH 1764 Under the Microscope 250 Years of Brown's Material Past
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ARCH 1764 Under the Microscope 250 Years of Brown’s Material Past Prof. Clyde Briant Office hours Wednesday 4:00-6:00 pm 220 Barus and Holley Prof. Brett Kaufman Office Hours: Tuesdays, 2:00-4:00 pm Rhode Island Hall 007 TA Susan Herringer This presentation and the images within are for educational purposes only, and are not to be distributed Week 10 Ceramics Lecture Ceramics – General Characteristics • Compound between metallic and non-metallic elements • Most common are the oxides, nitrides, carbides – e.g. Al2O3, SiO2, SiC, Si3N4 • Others are clays and minerals • Glass and cement • Carbons General Properties • Strong and stiff • Extremely brittle • Good thermal and electrical insulators • Corrosion resistant Classifications • Clay products – structural clay products (bricks, tiles, sewer pipes) – white wares (porcelain, china, tableware) • Refractories – Silica and alumina mixtures – Used for furnace linings • Abrasives – SiC, WC, Al2O3 • Cements – clay and lime bearing minerals • Advanced ceramics – MEMS, sensors, optical devices MEMS Systems Characteristics of Clays • Basic clay minerals are aluminosilicates such as kaolinite • Hydroplasticity – when water is added they become very plastic; water goes between the sheets and forms a film around the clay particles and lubricates them. • Also contain minerals that are non-plastic such fine quartz. This material fills spaces between the clay particle • Fluxes, such feldspar, melt when heated and form a glass which helps densify the resulting ceramic http://www.ihrdc.com/els/ipims- demo/t26/offline_IPIMS_s23560/resources/da ta/G4105.htm Processing of Clay Products • Hydroplastic forming such as extrusion of the wet clay • Slip casting – http://www.dynacer.com/processing/slip-casting/ • Tape casting http://www.ltcc.org.pl/about-ltcc/tape- casting/ Firing and Drying of Ceramics • Drying – removes the water to produce green ware. • Firing – 900 – 1400oC – Density and strength increase – Allows vitrification http://cool.conservation- us.org/jaic/articles/jaic21-01-001_appx.html Powder Processing • Powders shaped in a high pressure press • Sintered at an elevated temperature where individual grains fuse together. http://ceramics.org/ceramic-tech- today/previews-of-the-latest-articles-in-the- journal-of-the-american-ceramic-society-3 Archaeological Ceramics Ceramics are extremely passive meaning they weather very slowly and are nearly indestructible in soils where other materials deteriorate more rapidly. Carthaginian mask Early ceramics were used for practical applications such as cookware and amphora for storage, and also for ritual or artistic purposes thanks to a high plasticity of fine- grained clays before firing Glossary of technical terms Temper: natural or intentional addition of nonclay and non-plastic particles such as rock fragments, sand, slag, and organics such as chaff, seeds or seed husks, ash, lime or shell, or small bits of broken ceramics known as grog Plasticity: ability of a clay to be molded and maintain its shape, plasticity increases with smaller particles and more organic materials Slip: liquid mixture of clay applied as a decorative coating before firing Burnishing: rubbing a hard tool, like a stone or broken potsherd, over the surface of a spinning vessel to alter its appearance Wasters: failed vessels that collapsed or deformed during firing process Compression stress: pressure exerted on vessels through stacking Impact stress: pressure exerted on vessels through dropping or banging Thermal stress: pressure exerted on vessel through heat Levigation: a process of using water, traps, and channels to sieve clays in order to separate fine-grained clay particles from coarse ones. Carinations: sharp angles making up the shape of a vessel Flux: material that lowers the melting point of a glaze, such as lead, allowing it form a glass at lower temperatures. Carinations Categories of archaeological ceramics Rice 1987 Iron Age Phoenician jug (10th-8th centuries BC) Red slipped and burnished for a colorful, shiny appearance Slag tempered ceramic from Iron Age Levant (10th century BC), olivine/fayalite laths in vitrified clay matrix with copper prill (c) Vitrified ceramic olivine/fayalite inclusion Martin et al. 2013 Kaolinites – a very common two-layer clay that in its purest form is used for porcelain Smectites and Illites – three-layer clays frequently used for coatings or slips Rice 1987 Cretan potter demonstrating Clay mine for modern-day Tunisian potters coiling technique Ethnoarchaeology is used to study living potters which can inform on the processes of raw material acquisition, manufacture, use, and discard. When a “direct historical” connection can be made between an ancient and modern people, it may be possible to study the technology with a presupposition that it has continued uninterrupted since antiquity, but this is rare. Earliest fired clay “Venus” figurine from Dolní Vĕstonice, Czechoslovakia, 30,000 BC. Some of the other figurines made of fired and unfired clay had a temper of crushed mammoth bone. Therefore by the late Paleolithic people understood the concepts of plasticity, firing clay, and temper. Pre-Pottery Neolithic (PPN) denotes a time in the Near East and Levant from around 8300- 6000 BC when cereal agricultural started but before ceramic vessels were used. Walls of Jericho, PPN urban center (Bar-Yosef 1992) Near East, Mesopotamia In Turkey fired pottery begins by around the 9th millennium BC, but elsewhere in Near East it is in the 6th millennium BC that fired clay appears in abundance. By 3rd millennium BC stories such as the Epic of Gilgamesh relate the centrality of the concepts of harnessing the chaos of nature for the benefit of urban society. Samarran-ware pottery in Iraq dates to the mid- 6th millennium BC https://classconnection.s3.amazonaws.com/845/flash cards/87845/png/samarra_ware1320239668688.png Pottery may have been fired as early as 10,000 BC in Japan but firm evidence comes from mid- sixth millennium BC, called Jōmon pottery. Note the decorative techniques such as pinching. http://www.tufts.edu/programs/mma/fah188/ospina/jomon/ Middle Jōmon cooking vessel (2600-1500 BC) Kiln types Subterranean or above ground Sinopoli 1991 Rice 1987 In New World, pottery appears around 2500-2000 BC in Ecuador , Columbia, Pacific Mexico, and southeastern US. The high-speed potter’s wheel did not develop, and kilns were not widely used but instead hand-molded clay vessels were fired in open bonfires, so all are terra- cottas or earthenwares. Earliest American pottery from Ecuador, Valdivia around 2500 BC Chronology and geographic of early archaeological ceramics Rice 1987 References Bar-Yosef, Ofer. 1992. The Neolithic Period. In The Archaeology of Ancient Israel, edited by A. Ben-Tor. New Haven, Connecticut: Yale University. Martin, Mario A. S., Adi Eliyahu-Behar, Michael Anenburg, Yuval Goren, and Israel Finkelstein. 2013. Iron IIA Slag-Tempered Pottery in the Negev Highlands, Israel. Journal of Archaeological Science 40:3777-3792. Rice, Prudence M. 1987. Pottery Analysis: A Sourcebook. Chicago: University of Chicago. Sinopoli, Carla M. 1991. Approaches to Archaeological Ceramics: Springer US. .