The Sharp Scale was devised by Henrietta Sharp Cockrell as an objective and scientific way to measure the opacity-translucency of paper, particularly of manuscript folios, 'in the field' without specialized equipment, for example in a museum or library setting. The folio is held at a distance of 15 cm. from a constant 60 watt light source (such as an unshaded table lamp). A dowel (or pencil) is held behind and against it, creating a silhouette. Folios are added until the outline of the pencil is no longer visible. The number of the folios needed to obscure the silhouette of the pencil is recorded.