Distribution Measurement
Quality metrics track the consistency of the coating layer applied across the surface of a paper or board substrate. Maintaining coat weight uniformity ensures that every part of the web has the same level of ink receptivity, opacity, and barrier protection. Variation is typically measured in grams per square meter across both the width and length of the roll.
Print Performance
Irregularities in the thickness of the coating layer lead to mottled ink coverage and inconsistent gloss levels. When coat weight uniformity is poor, the absorption of the fountain solution or ink vehicle varies, resulting in visual defects in the final printed product. This is especially noticeable in large areas of solid color.
Production Control
Automated systems use infrared or beta-ray sensors to monitor the application in real time and adjust the metering blade or rod. Achieving high coat weight uniformity requires precise control of the coating color viscosity and the pressure of the application system. If the base sheet has an uneven surface profile, the coating will naturally pool in low areas and thin out over high spots.
Modern smoothing technologies help to mitigate this effect before the coating is applied. Consistent drying temperatures are also necessary to prevent the migration of binders. Monitoring the condition of the application blade prevents long-term drift in these values.
