This is Robert Cohen with the VOA Special English Development Report.
These days, stories about adobe are usually about Adobe, the California company that makes computer products. But this report is about adobe the traditional building material made of soil.
Adobe is shaped into bricks that can be placed on top of each other. They are used as a low cost way of making houses. They can substitute for other building materials such as wood and steel.
Adobe is soil that contains at least forty percent clay. In its purest form, clay can be shaped and stretched and used to make objects. Clay becomes very hard when it is put in a fire or a special oven.
Adobe becomes a sticky mud when it is mixed with water. Liquid adobe mixture can be poured into containers called molds. This way the adobe ca be shaped into bricks of the desired size. Adobe bricks must be completely dried before they are used. That is necessary so that the walls of a building will not shrink or break.
Too much water can make adobe weak. Sometimes other materials are added to the adobe mixture. These materials help keep the water in correct balance with the soil. This will help the adobe resist changes in the weather and humidity.
One material that is commonly added to strengthen the adobe is straw. Straw is the dried stem part of plants such as wheat, millet and sorghum. Straw is especially popular in places where the clay content of the soil is high. Other materials such as lime and cement can be added to strengthen the adobe. About once a year, houses made from adobe should be given a layer of mud. This "paint" job helps keep the adobe strong.
Adobe can take a long time to dry and become hard. So the bricks should be made in hot dry weather. If the weather is right, the bricks should dry in seven to ten days. People who work with adobe must experiment. They must find the right combination of soil mix, water content and drying methods.
Many people around the world have found that adobe is a low cost way to make a house or farm buildings. You can get more information about building with adobe from the organization Volunteers in Technical Assistance, or VITA. VITA is on the Internet at www.vita.org.
This VOA Special English Development Report was written by Gary Garriott. This is Robert Cohen.