Distribution of mass, or “Formation” is a critical property that influences strength properties, cockle and curl. Formation, using transmitted light, has been done on white paper for years but has been unavailable to paperboard and liner board due to the inability to use transmitted light. Now, a new method, pioneered by Dr. Steven Keller and Verity IA makes formation measurement to board manufacturers.
An excerpt from the paper
The in-plane distribution of mass, or paper formation, of paperboard products is a critical property that influences strength properties, cockle and curl, as well as the surface uniformity and print quality. While generating the uniform distribution of fibers in the forming section is of paramount importance, imaging and subsequent analysis of the web structure has been difficult. Few formation analysis systems have sufficient beam energy to penetrate paperboards that have grammages values exceeding 120 g·m-2 with sufficient sensitivity to determine mass variation at the spatial dimensions useful for characterizing the flocked structures.
This presentation describes the acquisition method for soft X-radiography that enables the capture of images suitable for advanced statistical and spectral formation analysis. One can discern individual fibers throughout the board structure with the high sensitivity and depth of field when film and scanner are used. The use of storage phosphor systems as the image detector enables the rapid imaging at more practical resolutions of interest to board manufacture. The ash content must be considered in order to avoid over estimation of the grammage by this method. An empirical approach that corrects for the presence of inorganic matter is presented. The results suggest that X-radiography is viable for imaging paperboard formation and that it may also be used to examine the size and distribution of internally contained mineral matter.