Auditing Analytical Test Scope Limits for Food Contact Board Certificates
Auditing food contact board certificates requires verifying laboratory test simulants, thermal parameters, and surface ratios against real package converting limits.
Ink Set-off
Transfer Mechanism
Unwanted physical transfer of wet printing ink from the front face of a printed sheet to the reverse side of an adjacent sheet occurs within a freshly printed stack. High mechanical pressure inside the delivery pile of an offset sheet-fed press forces wet ink film into direct physical contact with the unprinted reverse side of the top board. Ink set-off causes visual ghosting defects, sheet sticking and reverse-side contamination on converted paperboard stock.
Insufficient ink vehicle absorption or excessive ink film thickness accelerates surface ink transfer defects during high-speed printing runs.
Prevention Protocol
Press operators apply micronized anti-set-off starch powders across freshly printed paperboard surfaces to create mechanical separation between stacked sheets. Infrared dryers and hot-air knives accelerate oxidative ink film drying, reducing surface tackiness before sheets drop into the delivery stack. Adjusting stack pile height prevents excessive vertical pressure on bottom sheets, minimizing mechanical contact force.
Laboratory technicians measure ink set-off tendencies using standardized printability testers that apply controlled contact pressure against unprinted counter-strips at set time intervals.
Quality Threshold
Commercial acceptance criteria limit permissible reverse-side ink transfer on visual package surfaces and food-contact packaging linings. Set-off values exceeding visual density thresholds of zero point zero five optical density units indicate unacceptable reverse-side contamination. Heavy ink set-off on food packaging inner liners breaches food safety standards by introducing unbonded ink resins into internal package surfaces.
Uncontrolled ink transfer requires printer press speed reductions, ink formulation adjustments or complete pile racking interventions.