Paper having a higher than average thickness at par grammage. It can be used to increase the bulk of a publication with few pages. It is less transparent than papers of the same grammage and normal thickness. The apparent specific volume is the ratio between the thickness, measured with a micrometer, and grammage of a sheet of paper. For example, Acquarello paper 160 g/m² is 232 microns thic and consequently has an apparent specific volume of 1.45.