Capillary Sorption Anomalies under Dynamic Surface Tension Gradients in Recycled Paperboard Substrates
Dynamic surface tension gradients in recycled paperboard cause capillary stalling, uneven ink penetration, and severe converting spoilage.
Bristow Wheel Sorption
Sorption Analysis
Laboratory measurement devices for paper and board fluid dynamics track the immediate absorption of liquids on moving paper strips. The method known as bristow wheel sorption calculates the volumetric uptake of inks or aqueous coatings over contact times as short as two milliseconds. In this process, a liquid applicator head is held against a test strip attached to a rotating wheel of known speed.
The resulting track length of the liquid provides a quantitative measurement of the penetration rate under dynamic conditions before the paper surface becomes saturated.
Contact Dynamic
Pore structural geometry and chemical sizing influence the initial wet-up of the paper surface. Initial resistance to liquid wetting must be overcome during the first few milliseconds of contact in high-speed presses. The equipment determines both the wetting delay time and the subsequent absorption coefficient.
These parameters help board manufacturers optimize the starch or sizing applications at the size press to ensure consistent runnability.
Material Range
Rough paperboards and highly absorbent porous papers are not suited for this testing method. Extreme surface roughness allows fluid to escape beneath the applicator, which produces false readings of high absorption. The test remains most effective for evaluating coated printing papers and folding boxboards.