Binding in practice – the last link
Binding is the last link in the chain of operations which transform the paperboard into attractive and functional covers for brochures, annual reports, manuals, books, or magazines. This last link must be as strong as the others when it comes to the choice of paperboard product with respect to the binding methods at hand.
The most common binding methods for paperboard covers are saddle stitching, wire binding, glue binding, thread binding, and fadensiegel binding. In all of them, the fibre direction in the binding operation is essential. The folds of the cover (as well as the insert) must always be parallel to the fibre direction. This is necessary to achieve a durable bond, narrow and permanent fold lines and low folding resistance,
and to avoid waviness of the binding. A fully bleached paperboard provides the best results under difficult binding conditions, thanks to its long and strong fibres.
Saddle stitching is normally used for brochures, annual reports, magazines and booklets. The binding operation consists of creasing, folding and stitching. The folds must not crack as a result of the creasing and folding operations nor during subsequent use. This is particularly important if there is printing over the folds. Saddle-stitched productions put a lot of strain on that small piece of paperboard that holds the cover to the insert by the staple. By choosing a paper board made from virgin fibres, the risk of the cover becoming detached from the insert with use over time is minimised.
Thread stitching is the classic high-quality binding method. The sheets of the insert are stitched together in bundles with a linen thread. The block of bundles is glued directly to the back of the cover. When this binding method is used for paperbacks, it provides stability, durability and a high-quality appearance.
It is important to use virgin fibre paperboard with wire-O binding, which is often used for booklets and manuals. One practical advantage of this type of binding is that the printed insert can lay open when required. However, if the paperboard is too weak the cover can rip and fall off after intensive usage.
Glue binding, or perfect binding, is often used for booklets and paperbacks. Book covers need to be especially stable and durable. Depending on the thickness of the insert, creasing and folding can be carried out in various ways to improve both the function and the appearance of the cover. To achieve an attractive cover with distinct fold lines, a strong and sturdy paperboard with a smooth surface is required. However, to achieve a durable bond, the reverse side should be uncoated or the glue will not adhere easily. If the surface of the cover needs to be smooth and glossy on both sides, special precautions are required. When using UV varnish a glue area should be spared for better adhesion.
Fadensiegel binding could be regarded as a combination of
thread binding and glue binding. It resembles thread binding but is less expensive. It gives extra stability, durability and a high-quality appearance to the covers of printed materials such as large textbooks. The sheets are stitched together with a special plastic thread. The threads are melted and the insert block is glued directly to the back of the cover.
Saddle stitching puts a lot of strain on the
small piece of paperboard that holds the
cover to the insert by the staple.
There are a number of exciting alternatives
to classic saddle stitched materials; binding
can also help them stand out from the crowd.
A covered wire-O binding, gives a printable
spine for easy identification in the bookshelf.
There are various ways to crease and fold
Glue binding adheres better to an uncoated
reverse side. Extra creases on the front and
back enhances the appeal and quality.
An example of thread stiching.
The cover gluing operation
Gluing is not difficult but negligence in performing it can be costly. Either glue binding (where the sheets are folded, bundled and then milled to adhere better), or thread or fadensiegel binding (where the sheets are stitched, folded and bundled then the insert is glued directly to the back of the cover) can be used.
Types of surface
The result and type of glue needed depend on the type of surface to be glued.
The surfaces can be classified into three different types:
• Easy surface – uncoated or lightly coated.
• Demanding surface – fully coated, printed surface.
• Difficult surface – UV-varnished, film laminated or PE-coated surface.
Types of glue
The most common types of glue for bookbinding are cold glues:
• Polyvinyl acetate (PVA) for easy surfaces.
• Ethylvinyl acrylate (EVA) for easy, demanding or difficult surfaces.
• Co-polymers for difficult surfaces.
Important factors to consider when gluing are:
• The glue must wet and adhere to the substrate.
• The glue must be applied in the right place.
• There must be enough glue to form a good bond but not too much so that it squeezes out.
• The open time must not be too long.
• The pressure must be maintained until the bond is strong enough.
• The glue must meet the demands of the binding machine regarding correct temperatures and rest time before the book is removed from the machine.
Trimming is important to ensure a good cutting result without risking delamination of the edges. Parameters to be closely controlled are the pressure on the book, the knife sharpness and lubrication, and the wear of the plastic counterpart.
Key paperboard features
The paperboard features required for achieving successful binding are strength and resilience, consistency in flatness and stability, and good cutting, creasing, folding and gluing properties.
The paperboard properties generally required to achieve successful binding are uniform strength, consistency of flatness and stability, and good cutting, creasing, folding, and (when applicable) surface properties suitable for gluing. When using saddle stitching or wire binding, the strength is especially important. Saddle stitched operations put a lot of strain on the small piece of paperboard that holds the cover to the insert by the staple. When glue binding, a paperboard with an uncoated reverse side is the most suitable choice.
With well-controlled trimming, delamination of the edges can be avoided. Click to enlarge.