Water-based gravure surface printing ink for plastic films is the go-to choice for food, beverage, pharmaceutical, and export packaging demanding high environmental compliance. But it behaves differently from solvent-based ink on press. Here are nine practical points to get it right.
1. Dilution Ratio
Use deionized or distilled water for dilution. A specialty diluent can be used when needed. The recommended ratio is ink : water = 10 : (2鈥?). Adjust for specific print requirements, but don’t exceed the upper limit 鈥?going too thin causes print defects.
2. Substrate Surface Treatment Requirements
Water-based ink needs higher surface energy than solvent ink to wet and bond. Substrates must meet these minimum surface energy levels:
- PET film: 鈮?38 mN/m
- PE and PP film: 鈮?40 mN/m
- PA (nylon) film: 鈮?42 mN/m
3. Cylinder Selection 鈥?Use Shallow Plates
Water-based gravure ink is high-solids, low-viscosity with color strength 20%+ higher than conventional solvent ink. Use gravure cylinders with cell depth no more than 30 渭m. Shallow cells deliver: faster drying, lower ink consumption, and reduced per-unit cost.
4. Drying Conditions and Press Speed
Keep hot air temperature at 45掳C or above and extend the drying tunnel where possible. Water evaporates slower than organic solvents 鈥?adequate heat and dwell time are non-negotiable for preventing blocking and maintaining line speed.
5. Press Stops and End-of-Run Cleaning
Once fully dry, water-based ink does not re-dissolve in water. If stopping for more than a brief pause, or at end of run, clean the cylinders immediately and wipe dry with a clean cotton cloth. Dried ink clogs cells permanently and can corrode metal cylinders.
6. Ink Circulation and Leftover Storage
Use an ink circulation pump or submerge the pickup hose directly in the ink. Seal leftover ink with a lid 鈥?exposed water-based ink skins over and thickens quickly.
7. Storage Conditions
Avoid freezing and high-temperature exposure. Both degrade ink stability and performance.
8. Ink Mixing Rules
You can mix inks from the same manufacturer freely in any ratio 鈥?stir continuously while blending. But never mix inks from different manufacturers. Incompatible formulations cause degradation and unpredictable press behavior.
9. Removing Dried Ink
Since water-based gravure ink becomes highly water-resistant once dry, use ethanol or concentrated laundry detergent solution to remove hardened ink from cylinders and press parts.
References
- Wikipedia: Water-Based Ink 鈥?Composition, drying mechanisms, and environmental advantages over solvent-based inks
- Wikipedia: Rotogravure 鈥?Gravure printing process fundamentals including cylinder engraving and cell geometry
- Wikipedia: Surface Energy 鈥?Relationship between surface energy and ink wetting/adhesion on polymer films
- ISO 12647-4 鈥?Gravure Printing Process Control: International standard for process control in publication and packaging gravure printing
- NAPIM 鈥?National Association of Printing Ink Manufacturers: Industry standards and technical resources for water-based and UV ink technologies