Thickness (mm) ISO 534
A paper’s thickness is measured in micrometers (µm) – thousandths of a millimetre – and is the distance between the paper’s two surfaces. Thickness is in many ways an important consideration in paper selection, as it affects the stability, feel and of course thickness of the final printed product.
Bulk (cm³/g)
Bulk is the inverse of density, i.e. the number obtained by dividing the thickness of paper expressed in microns (1 µm = 0.001 mm) by its grammage expressed in g/m2. Paper is said to bulk well when the thickness seems high for its grammage and to bulk low when the reverse is the case. A high bulk stands for a less compact sheet.