Experience from preparation and investigation of clay microstructure

Clays without expanding minerals can be prepared so that their microstructural constitution is preserved. If expansive clays are treated in the same fashion there is an obvious risk of very significant distortion of the particle arrangement because of drying, expansion and disintegration. It is also a risk that impregnated clay becomes too soft to be cut for microscopy, but experience shows that embedding in a suitable plastic monomer with subsequent polymerization gives sufficiently hard specimens to make ultramicrotomy applicable. Impregnation with this substance requires that the pore water is first removed, which can be done in several ways as described and discussed in this paper. The thickness of the thin section should be as small as possible for transmission electron microscopy, i.e. a few hundred angstroms, but thicker sections can be used for certain microstructural analyses.