What you need to know while choosing Book Covers
In most cases, the design of the book cover is a designer/artist’s job. The publisher takes plenty of effort in the design of the book cover, which improves the salability, and shelf appeal of the book. The illustrations, photographs and designs on the cover are alloted a lot of importance; a huge number of hours are spent on discussing and designing the cover.
All these efforts can come to a naught, if the same attention is missing in selection of the material for the cover. Many of the publishers are aware of the important points to be considered while selecting the cover material/paper. However, some will give undue importance to aesthetics while ignoring the need to crease/score the covers. And finally there are others who will opt for cost over grain direction.
Let us discuss the considerations for choosing the “right cover” for a perfect binding job. Generally, the covers are thick, printed, embossed, laminated papers or boards. While selecting the cover materials, the following properties are to be considered :
* Thickness and size of stock
* Grain direction
* Suitability for creasing / scoring
* Splitting strength
* Inside surface properties
* Stiffness and trim strength.
1. Thickness & Size of Stock: Using a thick board to bind a thin book block is a strict "No No". The cover weight (gsm) is directly proportional to the book thickness. Please consider the guideline in the table below:
Book block thickness (in mm) Cover thickness (in gsm) *
Up to 5 mm 150 - 180
6 to 12 mm 200 - 230
13 to 16 mm 250 – 270
More than 16 mm 300 - 350
The spine length of covers should be foot plus 3mm and head plus 2mm, meaning that an additional 5mm longer that the book block.
* There are other factors like stiffness that need consideration while selecting the cover weight.
2. Grain Direction : The grain direction of the cover should be parallel to the book spine. This is absolutely necessary for a ‘well bound’ book
3. Suitability for Creasing / Scoring : A lot of stress is put on the cover board when it is scored. The two centre scores are necessary for achieving a square spine. The outer creases/scores are known as ornamental or opening creases and they power the opening of the covers. The scoring/ creasing lines, achieved through discs on the perfect binder, should not break the cover surface. Conversely, the cover should not be too thick for the scoring discs to create any impact. In cases, where the ornamental scores are not deep enough, the load of opening will shift to the second and third page and this can break the joint.
4. Splitting strengths : Splitting is a case where the outer layer of the cover comes off the next layer. When splitting occurs on the spine area or at the trimmed edges, it could have disastrous results. Cover materials are fabricated through different methods like couching (pronounced as ‘cooching’) or gluing of several thick layers. Couching is a process of attaching two or more paper webs into one layer, when they are moist, during the paper manufacturing. There is no glue used in this case. Hence couched type paper will have better split resistance when subject to moisture. Also, a high splitting strength will reduce the possibility of wrinkles on the book spine. It is ideal to make a few dummies with the available cover material and compare the results.
5. Inside surface properties: The surface of the inside cover is the one that comes in contact with the glue. There should not be any lamination or lacquer at the spine and side glue areas. Glossy cover should be tested for compatibility with the hot melt adhesive used.
6. Stiffness and trim strength: Extremely stiff covers will not travel well on a perfect binder. The same is true for very thin and highly flexible covers. In certain cover material, the coating, ink, lamination etc peel off at the edges during trimming. This means the paper layer will start to split. This is due to a low trim strength of the cover material.
There are few more points to be considered while selecting a cover, but the six points (listed above) are the critical ones. I've always believed that print buyers are aware of these criteria and take care of the same while suggesting the cover material. However if they do not, it is the responsibility of the book printer to bring these facets to their notice. If the print buyer still insists on the “wrong choice of cover” for whatever reason, then the job should be accepted with the risk factored in.
Additional care will be needed for setting the machine, in process and final inspection. This will mean more machine and man-hours as well as increased allowance for wastage. A costly affair, right?
Let us disregard the old adage about not judging a book by the cover!
