Surface area is a physical property you will see listed on the data sheets of many materials. Individual materials can contain particles that have a wide range of sizes, shapes, densities, surface texture, reactivities and unique chemistries and mineralogies. More than any other material, the physical properties of plastic clays and clay-containing slurries are directly tied to this. In clays, the total surface area of all particles in a sample help explain important physical properties, especially plasticity and drying shrinkage. The smaller particles are the more they interact with each other (and any water between them). In clays, more surface means a greater ability of the clay to exhibit plasticity. Water acts as a glue, holding all the particles together because the surface chemistry of clay particles has an electrolytic affinity for water. The total forces by which they attract to it increase, often exponentially, as surface area does. Kaolins have comparatively large particles compared to ball clays and thus have a much smaller surface area. Bentonites have an even smaller particle size and a much larger surface area than ball clays. Only a gram of a plastic clay can have many square meters (even dozens of square meters) of surface area, orders of magnitude more than low plasticity materials.
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