Double fan binding is a tweak on perfect binding. Rather than just having glue applied to the roughened edges of the book block, the loose pages are fanned one way and glue is applied, then they are fanned the other way and glue applied again. Thus the glue’s adhesion surface is not just the milled* spine, it’s the spine plus a tiny bit of the face of every page in the volume. With modern efficient adhesives this is pretty strong.

Here’s a promotional video showing how it’s done. If you look for double fan binding on YouTube you’ll find hand binders doing the job manually.

If you don’t see a video here, please click on the title of the post in order to view it in your browser.

Ultra fan or Ultra bind are the names by which this method tends to travel in the book business. Originally the UltraBind machine was designed for library repair work — in the video you can see books of different thicknesses and trim sizes going through one after the other. That they are destined for case binding is shown by the insertion of endpapers at the start. The system will of course work equally well for paperbacks, though it’s only recently that libraries have started holding them, and they probably don’t often judge it worth the money to rebind them.

In the dim and distant library repair was an exclusively hand-craft job. Loose stitching would be removed and replaced by new tighter sewing picking up the same thread holes as in the original binding. Such skills now cost too much and libraries have accepted that they have to get their books rebound without sewing. This means the cutting and grinding off of the spine fold, resulting in tighter gutter margins: this no doubt hastens the next visit of the book to the library repair binder as readers strive to crack open the spine. (Readers: please never do this to a book. Your job is to read it, not to test its endurance to pain.)

The machine can be used for short runs of new books, and is the basis of publishers’ ability to keep old books in print for ever via the magic of print-on-demand.

You can get to other entries in this binding styles series via the Index which can be reached via the tab at the top of the page.

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* Milling just means grinding off the edge of the pages to roughen them so that the fibers in the paper are raised and can bond more strongly to the glue. The bond is further enhanced by notching the spine.