Clay
The text of clay tablets is usually cuneiform, which is read by fewer than 300 people in the world today. Because it is a writing form, speakers of different languages used it and it has had many variants over the last 3,000 years. There are significant cultural reasons why clay tablets are important. Clay tablets first made their appearance in Uruk (southeastern Iraq) in 3,300 B.C. Over the centuries, they became less pictographic and more abstract, so that they were used as symbols for spoken language conveyed by the end of a reed pressed into the clay surface.
Clay was a good medium as it preserved fine lines and enabled a great deal of information to be captured in a small area. Clay tablets are quite small and fit easily into one hand, although the cuneiform was also used on other surfaces such as pillars. Clay is a hydrated aluminum silicate that is pliable when wet and can be softened with water and remolded when hard. Clay becomes rigid in the presence of heat. Tablets were often baked for durability, thus enhancing their ability to survive—they have survived fires without harm.
There are around 500,000 tablets known to exist today. Because of the variable surfaces of the tablets, it is rarely possible to reproduce the text. Consequently, scholars have had to travel to the site where they are kept in order to see them. However, advances in 3D imagery have allowed them to be digitized. For example, the United States Science Foundation has funded Digital Hammurabi, a project to create a permanent record of texts.
Identification
Clay tablets may be easily recognized by their size and general appearance, and may be distinguished from stone by the consistency of the material.
Condition Concerns
There are three types of clay tablets that may be presented for treatment: baked clay, unbaked clay, and clay that was poorly baked originally. Some clay tablets were originally inscribed then left to bake in the sun and some were further kiln fired. Clay absorbs salts which will tend to crystallize after excavation and cause deterioration which may only be stabilized by re-baking and washing.