The blistering is due to the poor bonding (not due to the whole web poor bonding). Liner is partial bonding well with medium, but there is still unbounded area which makes the liner separate from the medium in irregular bulge. Supposed that the blistering is due to the machine break down and adhesive agent problem, then the phenomenon is linked with double facer and the main reasons lie on the temperature, tension and heat plate temperature.
The liner blistering means that the board web temperature is uneven, or there is wet texture, under which conditions the board liner is heated and the extra moisture will become more steam when the board is going through the heating plate. If the steam cannot release out or onto the corrugator belt by the two ends of the corrugated medium, the pressure induced here will destroy the board viscosity which causes the blistering, because there is much moisture in the adhesive agent but the steam exit is narrow. Furthermore, the corrugator belt is contaminated by glue or oil which affects the absorption and elimination of the corrugator belt.
When the tension in uneven along with the direction of the web, it will cause the poor bonding, and when the moisture is released out, the viscosity will be destroyed which causes the liner blistering.
Heating plate temperature
The uneven temperature of the double facer heating plate will cause uneven release of the adhesive agent moisture which will destroy partial bonding of the board and induce liner blistering.
There are other reasons which will also cause the blistering like gelatinization, viscosity, etc. it is almost impossible to have no blistering. But we can reduce the blistering rate to the lowest point which is possible for us to achieve.