(Only on coated papers)
Causes
- Too high moisture content in the paper
- Too low z-strength
- Basis weight (higher is more critical)
- Porosity of the coating, not letting the moisture to escape
Occurs when water vapour can not evaporate fast enough through the coating layer in the dryer section of the heat-set press.
Recommended solution
- Try reducing the dryer temperature
- Try to reduce press speed. This will slow the moisture vaporisation and permit the water vapour to escape through the pores in the coating.
- Increase the press speed without increasing the dryer temperature as this allows the paper to be in the oven for a shorter period of time.