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Surface Area


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.

Out Bound Links

  • (Glossary) Particle orientation

    Clay particles are flat and prefer to orient or arrange in a lattice-like pattern during mixing and forming operations. In bodies where they mix with other non-clay ingredients, they continue to arrange to the extent to which they can tolerate the disruptions of the others. The smaller the clay part...

  • (Glossary) Ultimate Particles

    Processed ceramic materials are typically ground to 200 mesh and feel very fine to the touch. With some you can detect some particle grains between your fingers. The amount of these "physical particles" can be measured by washing or shaking the ceramic powder through a sieve. Using water washing and...

  • (Glossary) Particle Size Distribution

    When minerals and mixtures of minerals are ground into a powder a particle size distribution is produced, that is, populations of particles of various sizes. The relative sizes of these populations can be measured to rationalize the behavior of the powder in the ceramic process. Wide distribution...

In Bound Links

  • (Glossary) Water

    There is a need to discuss water in ceramic production as it related to a number of natural phenomena and production processes: Plasticity: Clays are plastic because water glues and lubricates the particles. The micro-dynamics of this are complex. Rheology: Suspensions (solids:water systems) e...


By Tony Hansen




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