Bent Lamination: Principles and Process
Bent lamination produces curved wood components by gluing together many thin strips of wood over a curved form. Each thin strip can bend elastically to the curve without breaking; when glued together and cured, the assembly becomes rigid and permanently holds the curve even after the form is removed. This is fundamentally different from steam bending (which bends a single thicker piece by temporarily plasticizing the lignin with steam) — bent lamination produces more predictable, precise curves; more variety of wood species can be used; and the final piece has greater dimensional stability because adjacent laminations have alternating grain orientations that resist springback. Maximum lamination thickness calculation: the bendable thickness depends on the bend radius and the wood species. A practical rule of thumb for solid hardwood strips: thickness should not exceed radius ÷ 200 for reliable bending without breakage. For a 12" radius curve: 12" ÷ 200 = 0.06" (1/16") maximum lamination thickness. Thinner strips provide more reliable bending but require more laminations for a given final thickness. For a 3/4" thick final component at 1/16" per lamination: 0.75 ÷ 0.0625 = 12 laminations. Building the form: the bending form (male or female, depending on clamping approach) is made from MDF or particleboard layers glued and stacked to create a rigid curved surface. The form's curve must account for springback — wood fibers under bending stress partially recover when clamps are released. Springback amount varies by species (flexible species like ash have more springback than stiff species like maple) and lamination thickness. Adding 5–10% extra curve to the form compensates for typical springback. Apply wax or plastic film to the form to prevent glue adhesion. Apply a thin, even coat of glue to both faces of each lamination (PVA or urea formaldehyde for best creep resistance), stack the strips, place over the form, and clamp firmly at 6" intervals. Allow full cure (24 hours for PVA) before removing clamps.