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15.10.2019 / Ronald Reddmann

What you need to know about paper in perfect binding

The paper characteristics are of preeminent importance for good perfect binding. But that will not be anything new to you. However, I would like to take this opportunity to tell you about a few tricks from our many years of experience at Muller Martini. From practical experience and numerous damage case clarifications, we know how you can quickly identify problems in advance, for example during order acceptance, and then also take the necessary measures on your perfect binder.

The perfect binding quality is influenced by a whole range of paper properties:
  • Paper making pulp 
  • Fillers
  • Paper bonding 
  • Surface texture
  • Grammage, thickness and binding strength
  • Page pull 
  • Direction of flow and elongation 
I will limit myself to just a few important points here. You can find detailed information on each keyword in our whitepaper.
 
Paper making pulp and fillers
The tiny spaces between the intertwined fibers in the paper are filled with different proportions of fillers and glues. The more paper making pulp and the fewer fillers, the better the perfect binding. 

Less optimal binding results are achieved with the following papers:
  • With high groundwood content (short and brittle groundwood fibers)
  • With papers with a high wood content (weakly adhering fiber and filler particles)
  • With recycling paper, i.e. waste paper (short grain)
Wood-free papers with longer, flexible cellulose fibers are best suited for perfect binding, as the fiber composite is not destroyed by the book spine processing and less dust is produced.
 

Coated and matte coated paper
If the paper surface is additionally finished, it can be better printed. However, coated grades have a negative effect on perfect binding. Only the fibers of the base paper are authoritative for the strength of the perfect binding. The more stitch application or matte finish, the denser the paper structure and the poorer the bondability.
The thermoplastic behavior of the binder-containing coating masses also plays a role here. What exactly does that mean? The tools of the spine preparation stations produce heat. Thick products, in particular, may therefore become plasticized, i.e. the sheet edges are practically sealed. Here, a fiber rougher head is used.

Direction of flow of paper
For perfect binding, the direction of flow of paper is also extremely important. In bookbinding circles one speaks of correct and wrong direction of flow, which can be determined for example with a strip sample, a fingernail sample or a tear sample. Instructions on how to make these samples can be found in the whitepaper.

Processing papers with the wrong direction of flow has the following disadvantages:

  • Poor opening behavior 
  • Wave formation in the gutter, resulting in poor lay-flat behavior 
  • Glue application between the sheets 
  • Poor grooveability
Paper grades suitable for perfect binding
So what is the right paper for perfect binding? Nowadays, there are so many different paper grades that react differently to different printing processes that the focus in perfect binding has shifted away from the machine to the material and its correct use. In my opinion, the technical information for the printer about the printability of the papers used should actually be supplemented with the additional note “suitable or unsuitable for perfect binding.” Unfortunately, this is not the case to date.

Some brief additional information: It is especially important that the spine preparation tools are always in good condition (wear, adjustments, etc.). After all, the best adhesive can be applied, but the edge pull will only be as good as the preparation of the book spine.

However, we can offer a few guidelines as to which paper grades are particularly suitable for perfect binding. You can find this information and many more tips in our whitepaper, which you can download here

We hope you enjoy the read!

Your
Ronald Reddmann 
Product Manager, Perfect Binding Systems
Muller Martini AG
 

Tags: #mullermartini, #print, #tipsandtricks, #yourstrongpartner


15.10.2019

Ronald Reddmann

Product Manager, Perfect Binding Systems