Why Bookmobile Added PUR Binding to Our Printing Services

Standard EVA bookbinding glues do a great job on uncoated papers, but are questionable when binding really big books on coated papers. As we are getting more and more requests to print art books and fine art photo books, we set out to investigate alternatives to EVA and wound up buying a new binder which uses a different kind of glue: PUR.

The original bookbinding glue was “animal glue,” made from the bones and hooves of animals. It was used by the ancient Egyptians for woodworking, and written instructions for making it have been found dating to 2000 BC. The go-to glue for bookbinding for centuries, animal glue is still used in the library binding business. However, for other bookbinding purposes, modern synthetic glues are used.

We have been using three different synethetic glues for bookbinding: a hot spine glue, a hot side glue, and, for special projects, a cold glue. Each glue is specially formulated for its role in bookbinding.

Hot spine glue

The spine glue we have used for all projects until recently is a formulation of Ethylene-vinyl acetate, or EVA. Bookbinding machines have a metal “glue pot” where the operator puts solid chunks of EVA, which look like Turkish taffy. The pot heats up and melts the glue. During the binding process, a roller picks up the heated liquid glue from the glue pot and applies it to the spine of the book block as it passes over the roller. Then the cover is applied onto the book block in the nipping station. By the time the book is dropped out of the machine, the glue has started to cool and set, and book is safe to handle and trim within a few minutes.

Modern EVA glues are much stronger than the paper of the book as long as they are applied properly, and, importantly, as long as the book is not too big, and not printed on heavy coated stocks. EVA has a hard time sticking to thick coated stocks, and there is a risk of pages coming loose from normal handling and reading.

Hot side glue

Side glue, which is a different formulation of EVA, is used to hold the front and back covers of paperbacks to the first and last pages of the book, so the covers don’t flop open. The binding machine has a separate, smaller glue pot for the side glue, and two separate angled rollers that apply a narrow line of hot side glue to the edges of the front and back pages of the book adjacent to the spine. Side glue always remains a bit sticky even after it has set, so it can hold the cover tight to the book bloc without it becoming stiff. Unheated side glue is a translucent amber color.

We have four Horizon perfect binding machines that use EVA spine glue and also have a side-gluing apparatus that uses the side-glue formulation of EVA.

Cold Glue

For hardcover binding, we sometimes use cold glue, which, as the name implies, is never heated but is liquid at room temperatures as long as it is in a container. Cold glue is made of Polyvinyl Acetate, or PVA. It is related to household and carpenter’s glues like Elmer’s. PVA is water based, and is used in some of the same applications that in the past used animal glues. PVA is hand applied to each book block as the pages are fanned out at the spine so that the glue can be applied to the sides of the pages as well as the spine. Accordingly, the machine we use for this kind of binding is called a “fan binder,” and the process “fan binding.” Fan binding produces a super-strong, flexible, lay-flat bind, but it is very labor-intensive and thus suited only for projects where cost is no object.

Enter PUR Binding

We are producing more and more art and fine art photography books, often printed on coated paper. We have recently increased our maximum page size to 12″ x 12″ to meet customer requests, but as mentioned above, EVA glue has limitations when it comes to binding big heavy books on coated stocks. In some cases, we have had turn down jobs where we felt our EVA binders could not do a job we could be proud of.

Tony Houle, our bindery supervisor, holds a giant test book bound on our new PUR perfect binder and cased in.

Tony Houle, our bindery supervisor, holds a giant test book bound on our new PUR perfect binder and cased in.

New to the market in the last few years are binding machines using reactive polyurethane glues, or PUR, rather than EVA. PUR glues have the reputation of exceeding EVA glues when it came to heavy coated papers, so we did some testing, assembling huge 1200-page 12″ x 15″ book blocks on 100-lb. coated paper and binding them both on EVA and PUR binders. The PUR was clearly stronger, as well as being more flexible, which helps books lie open during reading. One downside of PUR is that it requires 24 hours of curing before books can be trimmed and packed, unlike EVA where the books can be immediately trimmed and shipped.

Our operations manager Dieter Slezak researched several PUR binders and visited facilities using PUR binders with our bindery supervisor Tony Houle and machine wizard Mark Rask. We settled on the Horizon BQ-280, a PUR binder based on the Horizon BQ-270 EVA binder, two of which we already own. We purchased the BQ-280 from Standard Dynamics, a great Minnesota vendor we have worked with many times in the past.

The new BQ-280 was installed a couple of weeks ago, and we did further testing to figure out the best way to run it. We are using it automatically for any book where the text is printed on coated stock. As EVA is excellent for uncoated stocks and PUR is both unnecessary for such applications and adds production time because of the extra curing required, we will only use PUR on books with uncoated text stock by special request at an additional charge.

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Don Leeper is founder and CEO of Bookmobile, which has provided design, printing, eBook and distribution services for book publishers since 1982.