How do I repair leather with adhesive so it stays flexible?

Leather repairs fail for a predictable reason: the repair is stiffer than the material around it, so all the flex concentrates at the edge of the repair and works it loose. Everything in a good leather repair is about spreading that flex — a patch larger than the damage, feathered edges, and an adhesive that stays soft.

Safety

What you'll need

• flexible leather or contact adhesive
• thin backing material — leather, canvas or a repair patch
• isopropyl alcohol
• fine abrasive paper, around 180 grit
• a blunt tool for working the patch into place
• flexible leather filler and colourant, for a visible repair
• clamps, weights or masking tape

Step by step

1. Establish what the leather actually is.Genuine leather, bonded leather and polyurethane-coated 'leatherette' look similar and behave differently. Bonded leather is ground leather fibre on a backing and it disintegrates rather than tears; coated fabrics peel in sheets. A patch repair works on real leather and is usually cosmetic on the others.
2. Work out whether it flexes at that point.A tear in the side panel of a bag flexes little. A crease across a car seat bolster or the top of a shoe flexes thousands of times. The higher the flex, the larger the patch needs to be and the more flexible the adhesive.
3. Cut a backing patch larger than the damage all round.At least fifteen to twenty millimetres past the tear on every side, with rounded corners. A square corner is a stress point and will start lifting. Thin leather, canvas or a purpose-made sub-patch material all work.
4. Abrade the flesh side of the leather and the patch.Around 180 grit, lightly, on the surfaces that will be bonded. This removes the finish and the surface oils and gives the adhesive something to key into. Do not abrade the visible grain side.
5. Degrease both faces with isopropyl alcohol.Leather is naturally oily and often has conditioner, wax or polish on it. Wipe both bonding faces and let the solvent flash off.
6. Work the patch in under the leather.Slide it through the tear with a blunt tool and flatten it out so it lies smooth on all sides. Any wrinkle in the patch shows through the face for ever.
7. Apply flexible adhesive to both faces and let it go touch dry.Contact adhesive is the usual choice: coat the patch and the underside of the leather, wait until both are tacky and dry to a knuckle, then press together. This gives an immediate hold with no clamping, which is what a curved item needs.
8. Close the tear edges and weight it flat.Bring the two edges of the tear together so they just meet, without overlapping, and weight or tape the whole area flat overnight.
9. Fill and colour the surface only after the structure is sound.A flexible leather filler worked into the tear line in thin layers, each allowed to dry, then colour matched and sealed. Filler is cosmetic and it will crack if it is doing structural work.

Tips

• Contact adhesive is the traditional and still the best general answer for leather, because it holds instantly on a curved surface and stays flexible.
• Never use cyanoacrylate. It stains leather permanently, wicks along the fibres beyond where you put it, and cures hard enough to crack the hide at the edge of the repair.
• For a shoe sole, the repair is a different job with different products — a proper shoe adhesive and clamping — rather than a patch.
• Feather the edge of any filler far beyond the tear, and build in several thin layers rather than one. A thick layer of filler is a rigid plate on a flexible material.
• Condition the leather around a repair afterwards. Dry leather cracks next to a repair because the repair is the only stiff part, and conditioning keeps the surrounding hide supple.

Common mistakes

• Butt-gluing the two edges of a tear together — There is almost no bonding area and it is loaded in peel. It opens again within days. The backing patch is what makes the repair work.
• Using a rigid adhesive or filler — The repair becomes the stiffest part of a flexible material, so all the movement concentrates at its edge and cracks it out.
• Cutting a square patch — Corners are where peel starts. Round every corner and the patch lasts several times longer.
• Trying to colour-match before the structure is finished — Any further movement cracks the colour coat, and you will do the cosmetic work twice.

Questions people ask