Troubleshooting I Cracks in the Coating Layer

The challenges of cracking

Cracks in the coating layer (cracking) result from tension. This tension arises if the coating dries faster than the printing inks. In contrast to the underlying inks, the coating becomes hard and immobile after the loss of water. As the inks go on drying and stay mobile, the mechanical forces cannot be tolerated by the hard coating layer any more. This results in cracks in the coating surface. The print image looks similar to a dried river bed.

Cracking is especially visible on areas with high ink coverage. Often, this problem only occurs when printed sheets are taken out of the pile as it comes to a „shock drying“. For the significant testing of cracking behaviour, please take various sheets out of the pile and leave them for some minutes before you control the sheet in the middle.

Solving the cracks in the coating layer

S​​tep by Step

1. Reduce your drying performance

Cracks in the coating layer are encouraged by the dryer‘s high energy input. Control and reduce your drying performance where necessary.

2. Please check your fountain solution settings

The emulsification of fountain solution slows down the drying of the printing inks. Check your fountain solution settings and adjust them where necessary.

3. Control the application of coating

The lower the viscosity of a coating, the thinner the coating layer (two-roller-system). The result: Cracks become visible very fast. In this case choose a coating with a higher viscosity or increase the amount of coating you apply. But be careful: If you apply too much coating, running disturbances or blocking can be the consequence.

4. Use retarders

Add TerraAdd Retarder G 12/111 to your coating. By means of this, you do not only slow down the drying of your coating, but also improve its running capabilities. Moreover, you reduce the danger of drying at the roller. Please contact our Technical Services for the correct dose. A dose which is too high may lead to a blocking of sheets in the pile.

5. Choose another coating

If all measures recommended here do not solve the problem, please contact our Technical Services.

6. Choose faster drying printing inks

If your printing inks dry very slowly in relation to your coating choose a faster absorbent alternative if possible. By means of this, you can bring together the drying behaviour of inks and coating.

Your checklist

Influence factor: Dryer
Measure: Increase performance

Influence factor: Fountain solution
Measure: Use less fountain solution

Influence factor: Coating viscosity
Measure: Control

Influence factor: Troubleshooting
Measure: Apply retarder

Influence factor: Anilox roller
Measure: Choose bigger anilox roller

Influence factor: Coating
Measure: Apply appropriate alternative

Influence factor: Printing inks
Measure: Use faster inks

Still have open questions? Contact us and we will support you with the application.

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