| What is porosity?
Porosity is an area of sponge-like texture in an otherwise sound metal casting. There are two types of porosity: (a) Micro-porosity: very small (almost invisible) interconnected air filled cells, often spherical in form. (b) Macro-porosity: larger flaws in the casting visible to the naked eye, can be spherical or sometimes in the form of "pipes" or tubes. These types of porosity are found as either "Blind Porosity", i.e., from one surface only and therefore not forming a continuous passage for liquid, or as "Continuous Porosity", i.e., stretching from one inner face to another thereby causing a leakage path, or "Totally Enclosed Porosity", which can not be reached by impregnation.
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