Working With Clay: A How-to Guide

This is the VOA Special English Development Report.

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.

It is also important to dry the clay containers slowly. This means that the highest temperature should not be reached too fast.

You can add materials to clay to gain desired results. For example, you can add sand to prevent tiny breaks or lines from forming in the finished product. But you should not use sand from the coasts of oceans. Instead, you should use sand from rivers or from other areas of land that are not near the sea.

You can usually find good clay in low areas of islands or land, especially if volcanoes helped form the land. Clay often exists in fields covered with some water. The clay will be found about one meter below the ground. River banks often also have clay about one meter or less under the surface.

You can recognize clay because it is very shiny when it is wet. You can also perform a test. Take some of the material and add enough water to it to make it seem like you are making bread. Then press it in your hand until it is about the size of an egg. It is probably clay if it holds together instead of falling apart when you stop pressing.

And that's the VOA Special English Development Report, written by Gary Garriott.

这里是VOA特别英语发展报道。

粘土几乎在世界上任何地方都能找到。粘土经过几千年风和水对岩石侵蚀而形成。岩石在物理和化学方面都产生变化。化学方面，钾和铝等元素被加入或带走。物理方面，岩石分解成越来越小的碎片。经过很长的时间，一些岩石就变为粘土。

粘土非常重要，因为它在世界各地被用来制作各种各样的器皿。陶艺家加入水以使泥土变得柔软，这样，用手工或机器更容易使粘土成形。随后，将其放入非常热的炉窑中进行烧制。这样，烧成的容器拥有坚硬的外表，可以使用许多年。

在许多国家，粘土由火山形成。这种粘土通常含有许多矿物质。所以，用火山粘土来烧制容器时，炉窑的温度比普通粘土要求更高。火的温度可以高达1400摄氏度。

对粘土容器进行干燥的过程需要非常缓慢，这一点非常重要。这意味着不能在很短的时间内升到最高温。

可以向粘土中加入矿物质以达到更加令人满意的效果。例如，可以向粘土中加入沙子，以免成品出现细小的裂纹或裂缝。但是，不能使用来自海洋的沙子。相反，应该使用来自河流或者远离海洋的陆地的沙子。

在岛屿或陆地地势较低的地区通常可以找到比较好的粘土，尤其是如果陆地由火山形成。粘土通常存在于表面有水覆盖的田地。粘土通常在地表以下一米的位置。河岸表面下一米或更浅的位置也有粘土存在。

粘土很容易鉴别出，因为粘土湿润的时候非常有光泽。你还可以进行测验。取一些材料，加入足够的水，就像做面包一样。然后在手中挤压至鸡蛋大小。停止挤压的时候如果没有散开，而是粘在一起，说明是粘土。