A transparent book jacket made of polyester film offers a number of benefits:
- A jacket protects the book cover from dirt and from scuffing as the volume is handled and shelved.
- A jacket contains powdery red-rotted leather and prevents it from rubbing off onto adjacent volumes.
- The cover and title of the book can be seen through the transparent jacket.
- Shelf labels can be attached to the jacket's spine rather than directly to the book, avoiding possible damage to the binding from unstable label adhesives.
Not all polyesters are acceptable. Only ones that have been tested and proven to be chemically stable for long periods of time should be used. The polyester film chosen should be free of plasticizers, ultraviolet inhibitors, dyes, and surface coatings so that the film does not interact with the material it is intended to protect and thereby hasten its deterioration. Mylar type D, manufactured by Dupont, and Melinex 516, manufactured by ICI, are acceptable for use on books. Four mil polyester is suitable for most books.
The best known and easiest-to-make polyester jacket is a simple wrap-around (Figure 1). Because it is not fixed in place on the book, a jacket of this design tends to shift out of alignment, especially when used on a large heavy book. This style jacket is sometimes held in place with tape or straps, which can cause other problems. Another disadvantage of the wrap-around jacket is its failure to cover the edges of the book, leaving them exposed and subject to abrasion.
A slightly more complex polyester jacket avoids these problems. It incorporates flaps which hold the jacket on the book and which cover and thus protect the edges of the book.
Instructions for Making a Polyester Jacket with End Flaps
When constructing polyester jackets, you will need a straight-edge, a bone folder, and either scissors or a mat knife. Cutting and creasing can be done on a self-healing mat or on a large piece of mat board or binder's board.
- Cut a piece of polyester with a vertical dimension equal to 1 2/3 times the height (H) of the book and a horizontal dimension 4 times the width (W) of the book plus the thickness (T) of the book (Figure 2).
- Wrap the polyester around the book so that the edges of the polyester are even with each other and the book is centered between the top and bottom of the polyester (Figure 3). Polyester has a smooth surface and care must be taken to make sure that the book does not shift, especially while being measured.
- Place the book on a clean work surface and open the polyester flat, being careful not to change the position of the book on the polyester film (Figure 4).
- Mark the position of the book on the polyester film by making dents with the point of a bone folder at the corners of the book and at both ends of the joint (Figure 4).
- Wrap the polyester over the book again and turn the polyester and book over being careful that the book does not shift on the polyester (Figure 5). Repeat step four.
- Using a straight-edge and bone folder, crease the polyester straight across connecting the dents as illustrated (Figure 6). Broken lines represent creases.
- When creasing the polyester, place the straight-edge on the film with its edge next to, but not covering, the two dents to be used as guides. Create a crease by pressing down on the point of the bone folder while pulling it along the edge of the straight-edge. The straight-edge should be held down firmly to prevent slippage. Without releasing the straight-edge, reinforce the crease by inserting the bone folder under the polyester and rubbing it firmly against the straight-edge (Figure 7).
- At all "a" locations (Figure 8) make a second crease parallel to the first, outside the first, and at a distance from it equal to the thickness of the book's cover.
- Cut as shown in figure 9. Unbroken lines represent cuts.
- Fold the polyester film at all creases. Make the folds sharp by burnishing them with a bone folder. Remember that closely spaced parallel folds need to be made at all "a" locations. After these have been made, shape them with your fingers until both folds take on a 90° angle (Figure 10). Dampening your finger tips slightly with a moist sponge will make this shaping of the folds easier.
- Wrap the polyester film jacket around the book, tucking the end flaps inside the front and back covers. Tuck the top and bottom flaps between the outer surface of the book cover and the polyester film (Figure 11). The top and bottom flaps will be visible through the polyester film jacket.
Polyester film is difficult to work with and you may need a few tries to construct the jacket correctly. Once you have mastered the technique, construction time is about 15 minutes per jacket, excluding set-up time.
NEDCC gratefully acknowledges the work of Margaret R. Brown in illustrating this leaflet.
Written by Richard Horton