A firm rock or mineral of which a thin section is to be made must first be sawed to obtain a slice approximately ⅛ in. thick. This is then cemented to a numbered glass slide with Canada balsam, pressing the slice at an oblique angle against the glass slide to eliminate bubbles. The slice is then ground on a rotating lap using IF silicon carbide and finally on a similar lap using #600 silicon carbide until the standard thickness of 0.03 mm is obtained, when the cover glass is cemented firmly to the section.
Friable rocks such as sandstones, clays, and shales must first be impregnated with Canada balsam or some other medium before sawing and grinding. Coals are treated with a mixture of two parts of Canada balsam and one part of marine glue. Kollolith and glycol phthalate are also used to cement the rock slice to the glass slide. Very friable rocks are impregnated with Bakelite varnish.