Why Viscosity Control is Critical
Ink viscosity is one of the most significant variables affecting print quality in flexo production. Even small viscosity changes cause measurable color density shifts, dot gain changes, and print defects. Yet viscosity is also highly sensitive to temperature — a 5°C change in ambient or ink temperature shifts viscosity by 10–15%, enough to cause noticeable color variation.
Target Viscosity Ranges
| Ink Type | Target (Zahn #2 cup) | Target (Din #4 cup) |
|---|---|---|
| Solvent-based | 14–20 seconds | 16–22 seconds |
| Water-based | 18–28 seconds | 20–30 seconds |
| UV inks | N/A (viscometer) | N/A |
Automated Viscosity Control
Manual viscosity checking (cup measurement every 30–60 min) cannot maintain the consistency required for premium packaging. Automated inline viscosity control systems continuously measure viscosity and add solvent/water to maintain target within ±1 second. Benefits: color variation reduction by 60–80%, labor savings (no manual checking), complete viscosity logging for quality records. LISHG offers integrated automated viscosity control as standard on King Series and optional on Master Series.
