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Working With Clay: A How-to Guide

andyg 于2007-07-29发布 l 已有人浏览
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&raquo Download Audio(mp3) By Gary Garriott 2007-7-29 This is the VOA Special English Development Repor

» download audio(mp3)
by gary garriott
2007-7-29

this is the voa special english development report.

clay

clay is found almost everywhere in the world. it is formed by the action of wind and water on rocks over thousands of years. the rocks change in both chemical and physical ways. chemically, elements like potassium and aluminum are added and taken away. physically, the rocks break down into smaller and smaller pieces. after a long time, some of the rock changes to clay.

clay is important because it is used around the world to make containers of all kinds. potters add water to soften the clay. this makes it easier to form into shapes by hand or by machine. then it is fired in an extremely hot stove. the result is a container with a hard surface that will last for many years.

in many countries, clay was formed from volcanoes. this kind of clay usually contains many minerals. so the fires to make containers from volcanic clay must be hotter than those used for non-volcanic clay. the fires may be as hot as one thousand four hundred degrees celsius.

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