How to Keep a Newly Rounded Book Spine from Flattening After Casing In

Start by distinguishing the spine of the sewn pages—the textblock—from the outer spine of the cover. Inspect the book at both head and tail. In a hollow-backed binding, these are separate surfaces: the University of Illinois inspection handbook specifically describes looking between the covering material and the textblock to inspect the spine lining. It also checks the textblock’s shape at both ends and whether the boards sit correctly below its shoulders. University of Illinois Bindery Handbook

For your next binding, record the end profile at four checkpoints. A quick pencil tracing or photograph from the same angle makes a useful comparison. The following sequence is a diagnostic aid derived from the construction stages, rather than a test that proves a single cause.

First visible change	What to investigate next
The unlined textblock relaxes immediately after rounding	Backing and the amount of sewing swell
The shape changes while the linings dry	Lining contact and support beneath the shoulders
The dry textblock changes when placed in the unglued case	Case curvature, spine width, and board fit
The shape changes after casing and pressing	Joint placement, pressing arrangement, and drying support

Do not change every variable at once. If the dry textblock already holds its shape outside the case, begin with case fitting and pressing rather than resewing the book.

Rounding curves the spine and produces the corresponding concave fore-edge. Backing then works the section folds outward from the center to create shoulders on either side. The dictionary distinguishes these operations and explains that backing helps retain the round by arranging the sections so they resist working forward. Rounding and backing, Bookbinding and the Conservation of Books.

If you have rounded the textblock without backing it, this is an important structural detail to revisit before blaming the case. Check for recognizable, reasonably even shoulders and a smooth curve at both ends. Shoulder dimensions must relate to the boards that will sit against them. Backing terminology and function

The appropriate shoulder angle depends on the binding structure. In his original Parchment over Boards workshop notes, Peter Geraty uses approximately 45–60 degrees and works progressively toward the shoulders with glancing strokes. That is a structure-specific example, not a universal angle for every casebound book. It shows why a sharper shoulder should not automatically be treated as a better one. Peter Geraty, Parchment over Boards

Swell is the extra thickness at the spine introduced by sewing thread or guarding. Some swell is needed for proper rounding and backing; excessive swell can cause buckling and poor shaping. Numerous thin sections can add substantial sewing swell, while paper hardness affects how much thread thickness the paper accommodates. Swell, Bookbinding and the Conservation of Books

Consequently, a book that will not hold the intended curve does not necessarily need more rounding. Examine the sewn block before adding linings: is the spine disproportionately thick, or is there very little material available to form the planned shoulders? For a repeat project, compare a small sewn sample using the same paper and section structure before committing to the next full textblock.

Treat that sample as a construction trial. Record the paper, sheets per section, thread, and board thickness, then judge the resulting round and shoulders together. There is little diagnostic value in changing the thread while also changing the paper and section size.

The Library of Congress manual instructs binders to mold linings closely against the spine, avoiding gaps and bubbles, then reshape and weight the textblock until dry. For a rounded and backed block, it places the shoulder over the edge of a bench or board, with the weight beside the shoulder. This supports drying without forcing the projecting shoulder onto a flat surface. It also specifies paper lining grain parallel to the book’s height. Library of Congress, Forwarding

Apply this principle at your bench: check the end profile after attaching each lining, arrange the support so the shoulder clears its edge, and inspect again when dry. If the round has already changed, resolve that stage before attaching the case.

For a thicker book, assess whether the chosen lining structure is sufficient. The Illinois handbook checks both complete lining adhesion and the presence of an additional paper lining on heavy or thick volumes. University of Illinois spine-lining inspection

Make the dry fitting a separate checkpoint. In Peter D. Verheyen’s German case-binding instructions, the spine width is measured with a paper strip following the curved surface from shoulder to shoulder, checked at both ends. The case spine is then rounded to match the textblock. German Case (Bradel) Binding

A straight measurement across the back does not describe the same path as a strip following its curve. Before gluing, seat the textblock in the case, close the boards gently, and compare the profile with your earlier record. If closing the case visibly changes the round, pause and investigate the fit.

Check the joints as well as the spine strip. Verheyen makes joint spacing dependent on covering thickness and explains that covering material must be worked into the joints. His dimensions belong to his particular construction; use the dimensions appropriate to the binding method you are following. Verheyen’s case assembly and fitting instructions

Prepare the pressing boards, joint-forming equipment, and interleaving before applying casing-in adhesive. The Library of Congress procedure sets the hinges, presses between brass-edged boards, and then continues drying under weight. It also directs the binder to keep the book closed after placing the board onto the pastedown. Library of Congress, Casing In

Pressing schedules vary with construction. Verheyen’s Bradel method uses a brief nip, changes the inserted cards, and finishes drying under weight. Follow a coherent method suited to your materials rather than combining a pressing time from one procedure with an unrelated setup. German Case (Bradel) Binding: Casing-In

As a practical check, look at the head and tail before tightening the press: locate the rounded spine, shoulders, board edges, and joint-forming edges. If you cannot see how the arrangement accommodates the spine profile, adjust the setup before proceeding. Increasing pressure is not a useful diagnostic step when the geometry remains uncertain.

For a completed book, inspect the closed end profiles, board seating, and joints before choosing a repair. Illinois’s inspection criteria provide useful targets: a properly shaped textblock at both ends, boards fitting below the shoulders, and parallel, consistently formed joints. University of Illinois quality-control checklist

If only the case has lost curvature, investigate its construction and fit. If the textblock itself has flattened, treat the problem as structural reworking. The Library of Congress forwarding sequence removes the case and spine materials before restoring the shape and relining. That supports returning to the relevant construction stage rather than trying to reshape the finished book through its cover. Library of Congress forwarding procedure

For the next book, keep the four checkpoint records beside your bench. Find the first stage at which the profile changes, correct that stage, and compare again before continuing. This gives you a practical way to refine backing, lining support, case fit, and pressing without guessing which operation flattened the spine.

• Bookbinding and the Conservation of Books: “Rounding”
• Bookbinding and the Conservation of Books: “Backing”
• Bookbinding and the Conservation of Books: “Swell”
• Library of Congress: Collections Care Section General Manual, Intermediate Treatment II
• Peter D. Verheyen: German Case (Bradel) Binding
• Peter Geraty: Parchment over Boards, revised 2014
• University of Illinois Library: Bindery Handbook