Clamshell Case Part 1: Base Tray Construction

A fine binding made of leather requires protection against dust, moisture, and handling. Clamshell boxes are the most common protection for fine bindings. The hinged structures act as storage of a fine binding and prevents  damage to the covers.

  1. Start with the finished book measurements – measure for height, width, and thickness of the book. It is not recommended to make a clamshell box until the fine binding is completed. Making the clamshell before the book is complete usually ensures the book will not fit in the clamshell case.
  2. Select a medium thick mill (davy) board to construct base and top trays. The thickness of the mill board is dependent on the size of the book. The larger the book the thicker the mill board needed for support and protection. The grain direction of the mill board is also important when constructing the bottom and top cases. The grain direction should run parallel to the length of the book measurement. It helps to draw arrows to indicate the grain direction of the board when you purchase the mill board. Many bookbinding suppliers, such as Talas, will label the mill board grain on the packaging – either grain “long” or grain “short”. Grain “long” means the grain runs parallel to the long side of the cut mill board. Grain “short” means the grain runs parallel to the short side of the cut mill board. The most common processed mill board is grain “long”. For the clamshell base tray, cut the base of the tray the width (shorter measure) of the book + 1 board thickness and the length (longer measure) of the book + 2 board thickness. The sides will sit on top of this base so be sure to add in the board thickness to the measurements to ensure the book will fit inside the tray. Position the sides on top of the base for strength and durability over time.
  3. Start construction of the case by building the base tray which is smaller than the top tray. Cut 2 short sides the width of the book measure plus 1 board thickness and the depth of the book + 1 board thickness. Cut a single back piece the same width as the length of the tray base + 1 board width.
  4. To assemble, glue the sides and back pieces to the tray base to create a tray with one open side. Pay attention to keeping the sides at a 90 degree angle to the base. Note: on the top tray instructions in Clamshell Case: Part 3,  I will show how to use a teflon-lined, template box to keep the sides straight when gluing the sides onto the base of the tray.  This tray will be the bottom of the clamshell box. The open side will face the interior of the clamshell box.

Next select the material for the clamshell covering. You can use paper, bookcloth, and leather or combinations of the three. Bookcloth is a durable, economical material commonly used for clamshells. Bookcloth, typically, has a paper backing to prevent glue from seeping through the cloth. It is useful to mark the measurements on the bookcloth backing.

  1. After the glued pieces of the small tray has set up, measure the 3 sides of the glued tray in a continuous measurement. Start from the top short side open end, around the back long side, to the other open short side and add about 1/2″ to 3/4″ to the ends of the measurement. This will give the length of the bookcloth. Enough material is needed to wrap around all three sides of the tray and to turn-in at the ends.
  2. The bookcloth height measurement is: 2 heights of the tray sides + 1 mill board thickness + 1/2″ to 3/4″ add-on for the inside and bottom turn-ins. Double check the bookcloth measurements by rolling the small base tray over the length of the bookcloth. Mark your measurements with pencil to act as a guide for paste up. Bookcloth is easily cut with utility knife and metal ruler for a clean edges.
  3. Brush PVA glue along the backcloth’s length of the bottom height measurement. Place the tray right side down on the glued bookcloth backing. Align the mill board edge and base with the bottom pencil guideline.

The tray sides are covered by rolling the tray along the length of the cut bookcloth.

  1. Firmly press the base tray on the start line of the bookcloth, keeping the base of the tray aligned with the bottom pencil guideline. Note: PVA glue will make the bookcloth backing “slide” around a bit. Be sure the tray base stays aligned to the pencil guideline.
  2. Roll the tray over the glued bookcloth onto the tray back side. Keep the corner tight and the base of the tray aligned with the bottom pencil guideline.
  3. Continue the rolling the tray to the left side, keeping the corner tight and the base aligned to the pencil guideline.
  4. Use a bone folder (a teflon bone folder is shown here as glue does not stick to it) to remove glue bubbles and smooth the bookcloth to the tray sides. Smoothing tip: start in the center on the tray back side and smooth to the corners. Then turn to the side and smooth from corner to open edge.

The bookcloth extends over the top and bottom of the tray. For convenience, the bottom turn-ins are completed first.

  1. On the bottom turn-ins, pinch the corners at 90 degrees and then fold over at 45 degrees. This will provide visual guides to cut excess bookcloth for the miter folds. Cutting the excess bookcloth off will create a flat base without bulk when the miter flaps are glued down.
  2. Brush on PVA glue on the bottom turn-ins. Pinch the corners together and smooth down the back and side turn-ins to the bottom of the tray base. Do NOT smooth down the corners yet.
  3. Cut the corners on a 45 degree angle about a board thickness above the tray base. The board thickness will be just enough to fold over and cover the corner without showing any of the mill board.

Finishing the bottom turn-ins.

  1. Using the bone folder, tuck the mitered back corner flap under the side corner flap on both sides.
  2. Smooth the turn-ins and flaps down with the bone folder. Place under weights for about 20-30 minutes to allow the glue to set up.

Read more in “Clamshell Case: Part 2: Covering Base Tray”.


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