Perforating, Creasing & Numbering
It’s important to remember that there are a few factors that determine the performance of paper. The structure of paper varies with things like printing type (offset ink or digital toner-based), coating thickness and fiber content. Although coated papers tend to reproduce originals better, they are also more susceptible to cracking. The inks and varnishes involved in the printing process contribute to making paper less flexible, and most digital print engines tend to dry out the paper - making the cracking issue more prevalent. Paper’s moisture content and the relative humidity of your environment also play a role. As such, the first strategy for minimizing the cracking problem is to examine these factors and make adjustments as needed.
Creasing Versus Scoring
The strategy for handling cracking problems in high-quality printing is creasing. Even if the factors listed above are all perfect, creasing (or scoring) may still be necessary for some stock. It’s worth noting that creasing and scoring, although often used interchangeably, are actually different. Scoring involves any method that reduces paper stiffness along a line, whereas creasing refers to the creation of a “paperboard hinge” via compression along the line where folding will occur.
Eliminating Cracking and Splitting
When sheets are bent at the crease, the force that would normally cause splits or cracks in the sheet are directed inwards instead. As the fold continues, a rounded bead is formed inside the fold to absorb all the force, keeping the folded piece smooth and unbroken. Although scoring can eliminate fiber cracks, as the sheets get heavier a stronger compression force is needed to prevent cracking. That’s where creasing comes in, and why it’s so important to the entire printing process. When done successfully, creasing helps you achieve a professional-looking product.