White fiber is exposed in a print when stretched or folded.
Why does grinning occur?
Ink is unable to fully penetrate the fabric likely due to the fabric construction, elasticity, or lack of saturation.
Quick Fixes for Grinning on Fabric
Ensure proper amount of ink is being printed to transfer paper.
Increase temperature and/or dwell time on heat press/calender (gradually) to force ink deeper into fibers.
Additional ink (saturation) and higher heat press/calender settings are likely more necessary for thicker, plush fabrics.
Best Fixes for Grinning on Fabric
Do what fashion designers do and lay out the print in the opposite direction.
SIMPLY ROTATE THE PRINT TO RESOLVE THE COMMON GRIN-THROUGH ISSUE.