Porosity describes the total pore volume found in a compact. Pore size distribution, however, describes the nature and distribution of pores that make up the overall porosity. For example, the moisture content in a sample suspension or paste is related to porosity. The ease of ovement of that moisture in forming and drying is related to pore size distribution. As another example, consider two fired ceramic specimens which have the same porosity. The first has one very large pore. The second has lOW micropores. The first specimen will have low mechanical strength, while the second will have high strength.