Ceramic Technology and Analysis

1. Ceramic Technology and Analysis

2. Clay and temper preparation

3. Watch out for salt!

4. Temper • As the clay in pottery dries, or is fired, the loss of water causes compaction of the clay platelets, which may cause cracking. • Temper is a material that is added to clay that resists shrinkage and is also refractory under the conditions of firing. It can take many forms, including grog, which is ground-up sherds.

5. Vessel Formation Techniques Technique Appearance PinchingThick-walled lumpy bowl Paddle and Anvil Irregular surface and shape SlabCylindrical shape CoilSmooth sided, asymmetrical Mold visible seam, appearance identical to other vessels. Slow and Fast Wheels finger striations in interior, symmetrical profile, thin walls in the case of fast wheel.

6. Cahuilla potter demonstrating the paddle and anvil technique

9. Steps in Vessel Formation • Digging and preparing clay, adding temper. • Forming the base (sometimes a mold is used, e.g. a basket). • Forming the walls, including scraping. • Applying impressed decoration while clay is still plastic. • Slipping pot while it is still damp.

10. 6. Drying. 7. Burnishing, painting, and glazing (if desired).

11. Degrees of Firing Temperature Term Appearance Sun baked Adobe mud w/ straw Below 900˚ Terra Cotta roof tiles 900˚-1200˚ Earthenware pottery 1200˚-1350˚ Stoneware Asian pottery Above 1300˚ Porcelain Fully vitrified Term: vitrification – to convert into glass

16. Prehistoric Kilns Left: Yarim Tepe Iraq, 5500 BC Below Bonpo Village, China 4500 BC.

17. Terms Related to Firing Environment • Oxidizing: a free flow of oxygen reaches the vessels during firing. Minerals in the paste, slip, and paint are converted to their oxide forms, causing color changes. • Reducing: Oxygen is cut off to the fire during the latter stages of the firing process. Additional carbon may be thrown onto to fire beforehand, and the carbon is driven into the fabric of the pot, turning it black. Minerals turn into their unoxidized forms.

19. Mug Jar Ollas Generally vases and mugs have unrestricted orifices (though the mug above has a restricted orifice), ollas and jars have restricted orifices. Vase

20. Amphora Bowl Note that it is common to paint the inside of a bowl. Pitcher Comal

21. crucible Pithoi lamp canteen

22. *referred to as the upper body by Anna Sheppard Common Ceramic Terms Relating to Vessel Form rim rim orifice orifice neck neck shoulder* body base base

23. Asian Ceramic Technology: Han Dynasty 206 BCE – 220 AD • Lead glazed pottery: low-fired pottery that uses powdered lead oxide as fluxing agent, mixed with quartz in a ratio of 3:1. Small amounts of copper were added that turned green when oxidized, or iron which turned brownish-yellow.

24. Celedon: an innovation of the the 1st century AD within the Eastern Han dynasty. Celedon is to be equated with porcelain in that it is fully vitrified. • The green color of celedon glaze was achieved by iron oxide and wood ash fired in a reducing atmosphere.

25. Porcelain • Porcelain is fully vitrified pottery made from Kaolin clay. It has to be fired at between 1200 and 1400 degrees celsius.