Flexographic Aqueous Latex Barrier Coating Viscosity Measurement Fundamentals
Flexographic aqueous latex barrier coating viscosity requires multi-shear rotational measurement to ensure accurate anilox transfer and barrier film continuity.
Efflux Cup
Gravity Rheometer
Viscosity measurement instruments that operate by timed liquid drainage through a precision orifice provide a rapid method for assessing fluid flow in production environments. Technicians use the efflux cup to monitor water-based inks and varnish coatings directly beside the printing press or coating station. The time required for a specific volume of liquid to pass through the lower opening relates directly to its flow resistance.
Testing Procedure
Operating this device requires filling the vessel to the brim while blocking the bottom nozzle with a finger. A stopwatch starts the moment the finger is removed and stops at the first break in the continuous stream of exiting liquid. This transition from steady flow to droplet separation marks the end of the test, and the total elapsed seconds represent the viscosity rating.
Temperature affects this measurement, meaning that the test must occur at a standardized reference point to ensure repeatability across different shifts or seasons.
Pressroom Calibration
Correct ink flow prevents printing defects such as misting on high-speed rollers or inadequate coverage on the paperboard substrate. If the drained time is too short, the ink is thin, leading to washed-out colours and excessive penetration into the paper fibres. Conversely, thick inks cause picking and build-up on the printing plate.
This benchtop draining test allows operators to adjust the mix on the fly by adding solvent or varnish until the drainage time falls within the required tolerance.