Folding a paper signature

A signature is a small group of folded sheets — typically four or five folios nested inside one another — that forms one section of a finished book. Folding a clean signature is the first real skill in book-binding, because a signature that folds badly stitches badly and trims badly. This tutorial shows the folding sequence that produces a tight 8-folio signature in about 10 minutes.

Materials

| Item | Specification | Quantity | |---|---|---| | Paper | 120gsm, A4 | 4 sheets | | Bone folder | Bovine or 4mm PTFE | 1 | | Clean work surface | — | 1 | | Weight | 5kg | 1 |

Steps

1. Square each sheet by aligning it precisely to the edge of a table.
2. Fold the first sheet in half by bringing short edge to short edge, press with your finger, then burnish with a bone folder from the centre out.
3. Open the sheet flat and check that the fold is a single crisp line.
4. Fold the next sheet the same way and nest it inside the first along the fold.
5. Continue until four sheets are nested. This gives one signature of 16 pages (8 folios).
6. Burnish the nested fold along the spine once more with the bone folder.
7. Tap the head and tail of the signature on a hard surface to jog it square.
8. Place under a 5kg weight for at least 2 hours so the fold relaxes.
9. Re-check squareness after pressing and trim if necessary.
10. Store flat until you pierce for stitching.

What to watch for

• Paper grain matters. Grain must run parallel to the spine, otherwise the signature springs open after pressing. Fold a small test strip — it folds cleanly with the grain and cracks against it.
• Burnishing too hard scars the paper. Use the flat of the bone folder, not the edge, and apply moderate pressure.
• Nesting four sheets creates natural creep at the fore-edge. This is normal; you trim it at the end.

FAQ

How many folios should a signature have?

Four or five. Fewer and the book has too many stitching stations; more and the fold balloons at the spine and the inner sheet sticks out.

What is paper grain?

Paper fibres align in one direction during manufacture. Folding with the grain is clean; folding against it cracks the surface.

Do I need a bone folder?

For a single book, no — your thumbnail works. For any more than that, yes. A bone folder produces an order-of-magnitude flatter fold.

How long should a signature rest before stitching?

At least 2 hours. Overnight under weight is ideal and avoids spring-back at the fold.

Next: make a simple pamphlet binding, introduction to Coptic stitch, and the paper supplies page.