Explanatory notes
… they were obtained, and their edges are roughly trimmed and bevelled. Their thickness usually varies from 200 to … by rifting sheet mica. Like the sheets from which they have been rifted, they have the shape of irregular polygons. … marketed as : (1) Condenser film, usually of a thickness between 25 and 200 micrometres (microns), or (2) Splittings, …