Gary asks,
Could you tell me the key variables in the Litho Label and the Corrugate Board that will affect Label Fracturing. We are seeing fracturing variability in the litho label after laminating and scoring.
Moisture, paper grade and condition, glue/adhesive, scoring profiles, scoring rule, impression and the manufacturing process are some of the variables that can cause score cracking (fracturing) in both litho-label and corrugated. When a label is glued over a liner you’ve added another ply and basically reinforced that surface. Now, when that surface is scored and folded the label is stretched around the corrugated liner causing stress to the label causing it to tear.
Moisture may play one of the most key roles in score cracking. If the moisture level is too low, the paper loses its elasticity, the fibers become brittle and fail resulting in a cracked score. However, if the moisture level is too high, or there is too great a difference between the moisture levels of the corrugated and the label then you can risk warp and shrinkage issues.
In an earlier post on this topic Brian Tankersly from Lewisburg Printing offered insight through his experience with the affects of moisture on litho labels. Click here to read that post.
We tend to take great care of our litho-labels. We handle them so that are not damaged. We keep them in controlled environments to maintain moisture levels, cleanliness, etc, but do we take the same care to control and monitor the sheets to which the labels are being applied?
If the corrugated liner under the label tears, the result will most likely carry through to the label. So the condition and “conditioning” of both the corrugated and litho-label are critical to the quality of the score.
Then of course there is the paper itself. Every paper machine has its own unique profile and engineers each one of its products with its own DNA characteristics. As in life, there are tradeoffs to make: improving one property may diminish another. In the case of high graphic substrates as those typically used for labels, the formulas, combinations and engineering of the paper can be proprietary information. An example can be the hardwood to softwood fibre mix. The hardwood to softwood ratio is used to improve the coating application. However, enhancing the “coatability” of the paper can increase the incidence for score cracking. Also some types of coating can be more prone to cracking than others.
I hope this provides some help and variable to consider. If you have any further questions, or there is anyone out there that has information to contribute, please don’t hesitate to comment or contact us.
— Ralph
askralph 
December 2, 2015 at 11:51 am
Yes, Thank you very much! Gary
Sent from my iPhone
February 17, 2016 at 12:26 pm
It’s also worth checking if the varnish coating is UV or water-based. It often seems the UV varnished are less flexible. Assuming you are flatbed die-cutting, you should be using CITO matrix (a better choice than counter-plates) and die-cutting from the label side. This is particularly useful for 180 degree scores but be careful of dimensional loss if your design features roll-over lock tabs. Also, have you looked at grain direction?