Which glue should I use and how do I make it hold?

Matching adhesive to material, and the preparation and clamping that determine whether a repair lasts.

Difficulty: beginner
Time: 20 min
Read: 2 min
Safety: caution

Short answer

Match the glue to the materials: PVA for wood, epoxy for a strong gap-filling bond on most things, superglue for small non-porous items, and a flexible adhesive for anything that moves. Clean, roughen and clamp — preparation matters more than the glue.

Glue repairs fail on preparation far more often than on adhesive choice. A clean, roughened, well-clamped joint with an ordinary glue outlasts a poorly prepared one with an expensive product.

Safety

Superglue bonds skin instantly — keep acetone or nail polish remover to hand, and never use it near eyes. Two-part epoxies and solvent adhesives need ventilation. Read the label; some adhesives are flammable and some give off harmful vapour.

What you'll need

The right adhesive
Clamps or tape
Sandpaper (optional)
Degreaser (optional)

Step by step

Identify both materials before choosing.Wood to wood, plastic to metal, ceramic to ceramic. The combination determines the adhesive, and getting it wrong is why repairs fail.
Use PVA wood glue for wood.It is stronger than the wood itself when clamped properly. Nothing else is needed for a clean wood-to-wood joint.
Use two-part epoxy for strength and gap filling.It bonds most materials, fills gaps, and is structurally strong. It is the most versatile option when you are unsure.
Use superglue for small, close-fitting, non-porous repairs.Ceramic, hard plastic, small breaks with a good fit. It is brittle and does not fill gaps, so it fails on anything under load.
Use a flexible adhesive for anything that moves.Shoes, fabric, anything flexed or vibrated. Rigid glue on a flexing joint cracks within weeks.
Clean and degrease both surfaces.Adhesive bonds to the surface it touches. Grease, dust or old glue means it bonds to that rather than to the material.
Roughen smooth surfaces.Light sanding gives mechanical grip as well as chemical bonding. It makes a substantial difference on plastics and glazed surfaces.
Clamp it and leave it for the full cure time.Not the handling time — the full cure, which is often 24 hours. A joint disturbed early is permanently weakened.

Tips

Dry-fit the pieces before applying any glue. Discovering they do not align after the glue is on is a very common and avoidable problem.
Wipe excess glue immediately. Cured adhesive is far harder to remove and it prevents finishes adhering later.
For superglue on skin, warm soapy water and patience usually works; acetone dissolves it faster. Never pull bonded skin apart.

Common mistakes

Not clamping the joint — Most adhesives need pressure and close contact to reach full strength. An unclamped joint is a fraction as strong.
Using superglue on something that flexes or bears load — It is brittle and does not fill gaps. It fails at the first stress on anything structural.
Gluing dirty or greasy surfaces — The adhesive bonds to the contamination rather than the material. Cleaning and roughening is most of the job.

Questions people ask

What is the strongest glue?

Two-part epoxy for general strength and gap filling on most materials. For wood specifically, PVA wood glue makes a joint stronger than the timber itself when clamped properly.

Why does my glue repair keep breaking?

Usually poor preparation or no clamping, or a rigid adhesive on something that flexes. Clean, roughen, clamp, and match the adhesive's flexibility to the item.