Grease Evaluation
Laboratory evaluation of paperboard grease resistance measures the substrate’s ability to withstand the penetration of synthetic oils and solvents under controlled conditions. This standardized procedure, widely referred to as the kit test, utilizes a series of castor oil, toluene, and heptane mixtures of varying aggressiveness to rate the barrier performance. The resulting rating, ranging from one to twelve, indicates how effectively the packaging will prevent grease from staining the outer carton during storage.
It does not measure long-term barrier performance but provides a rapid benchmark for production quality control.
Test Procedure
Technicians apply drops of the progressively more aggressive chemical mixtures onto the surface of the paperboard for a specified duration, typically fifteen seconds. Once the time has elapsed, the liquid is wiped away, and the substrate is examined for any signs of wetting or penetration. The highest numbered mixture that fails to leave a mark or darken the board determines the final rating.
Performing a kit test is critical during the manufacturing of food-contact packaging to verify that functional coatings have been applied uniformly.
Practical Application
Packaging for fried foods or baked goods typically demands a high rating to maintain structural integrity. If the board rates too low, fats will migrate through the fibers and compromise the printed surface. This migration creates aesthetic issues and can weaken the glued seams of the carton.
