Density Inverse
International standard that specifies the method for calculating the thickness and apparent density of paper and board. The iso 534 bulk value represents the volume occupied by a given mass of the material. Measuring this value is necessary for determining the feel and stiffness of a sheet.
Arithmetic Result
Testing involves measuring the thickness of a single sheet or a pack of sheets under a specific pressure. Calculation of the iso 534 bulk requires dividing the thickness in micrometres by the grammage of the sample. A high value indicates a light and airy sheet, while a low value points to a dense and compressed structure.
The resulting ratio allows specifiers to understand how thick a book spine will be or whether a carton will feel sturdy in the hand.
Press Variable
Maintaining a consistent level of bulk is necessary for downstream printing and finishing equipment. Variations in iso 534 bulk can cause issues with vacuum feeders on a press or interfere with the fit of a product in its primary packaging. Calendering is the primary tool used at the mill to compress the web and reach the target level.
Too much compression can damage the fibres and lead to a brittle final product.
