TROUBLESHOOTING | Insufficient drying of waterbased coatings
The challenges of insufficient waterbased coatings drying
The drying behaviour of printing inks and coatings plays a major role in printing and further processing. If inks and coatings are not sufficiently dry, ink set-off or blocking of sheets in the pile may be the result. Also, colour abrasion and scratches are possible. A trouble-free further processing of the printed product cannot be guaranteed. Waterbased coatings (also called dispersion coatings) dry physically by means of the absorption of the coating into the substrate and the evaporation of water. This drying is achieved through hot air and infrared. With the drying, water is extracted from the coating. Polymer particles cross link with each other and form the coating film.
Solving Insufficient drying of waterbased coatings
Step by Step
1. INCREASE YOUR DRYER PERFORMANCE
The optimal setting of the dryer is individual (IR and hot air). Temperature in your pile should not exceed 35°C. Consider a sufficient airing also during the drying process. The dryer’s air contains water after a longer production period (humidity). If this water comes into contact with the printed sheets, inks and coatings may become wet again (laundry effect).
2. CHECK YOUR WATER/INK BALANCE
If too much fountain solution emulsifies into the printing inks (>25%), drying is slowed down. In this case reduce your fountain solution. If inks are emulsified, clean your printing press and adjust your settings.
3. REDUCE YOUR INK APPLICATION
A high application of inks slows down drying. If possible, reduce your ink application. Also, the ink type affects drying time. Fresh, low odour or migration less inks normally dry more slowly than oxidization drying inks. Choose faster inks if needed.
4. IS ANOTHER SUBSTRATE POSSIBLE?
Drying time also depends on the type of substrate. Choose a substrate with a faster penetration behaviour if requested.
YOUR SHORT CHECKLIST
Influence factor: Dryer
Measure: Increase performance, clean, change if necessary
Influence factor: Fountain solution
Measure: Use less fountain solution
Influence factor: Printing press
Measure: Reduce ink covarage
Influence factor: Substrate
Measure: Choose a substrate with a faster penetration behaviour
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