Wood glue

What Is Wood Glue?

Wood glue is an adhesive designed specifically to bond wood to wood. It works by soaking into the wood’s pores and forming a solid, long-lasting film as it cures. While many general-purpose glues can stick wood together, dedicated wood glues provide stronger bonds, better creep resistance (they’re less likely to slowly shift under load), and features tuned for woodworking—like reasonable working time, easy cleanup, and strength that often exceeds the wood itself.

Common Uses in DIY and Home Projects

Wood glue shows up across a wide range of tasks:
- Furniture repair: loose chair rungs, split table legs, wobbly joints
- Cabinetry and carpentry: face frames, drawer boxes, shelves, and casework
- Trim and molding: attaching returns, scarf joints, and miters (paired with nails)
- Panel glue-ups: edge-joining boards to make wider panels or tabletops
- Joinery: dowels, biscuits, mortise-and-tenon, half-laps, and finger joints
- Veneering and laminations: bonding thin layers of wood or plywood
- Crafts: picture frames, cutting boards (use waterproof, food-safe options), and wooden toys

Types of Wood Glue

Choosing the right type makes your project easier and more durable.

1) PVA (polyvinyl acetate)
- Often labeled as “wood glue” or “carpenter’s glue.”
- Yellow or white liquids that clean up with water.
- Strength: excellent for tight-fitting joints; dries rigid.
- Open time: typically 5–10 minutes; extended/open-time formulas offer longer.
- Water resistance: varies by product. Some meet ANSI/HPVA Type II (water-resistant) and a few meet Type I (waterproof).
- Best for: most interior projects, panel glue-ups, furniture joinery.

2) Aliphatic resin (yellow “carpenter’s glue”)
- A subset of PVA tuned for woodworking.
- Slightly better heat resistance and sandability than basic white glues.
- Very common in furniture and cabinetry.

3) Polyurethane glue
- Moisture-curing adhesive that foams as it sets.
- Bonds many materials (wood, metal, stone, some plastics) and fills gaps better than PVA.
- Water resistance: good for outdoor use.
- Cleanup: messy; use solvents before cure or scrape after.
- Best for: exterior joints, mixed-material repairs, less-than-perfect fits.

4) Epoxy (two-part)
- Mix resin and hardener; available in different cure speeds.
- Excellent gap filling and strong, waterproof bond.
- Adheres well to oily or exotic woods when surfaces are properly prepped.
- Best for: structural repairs, boat/outdoor projects, oily woods (teak, ipe), and where clamping is tricky.

5) Hide glue (hot or liquid)
- Traditional protein-based glue.
- Reversible with heat and moisture; great for antique repair and instrument work.
- Open time: short for hot hide glue; moderate for liquid hide.
- Best for: restoration, projects needing future disassembly, fine woodworking.

6) CA (cyanoacrylate, “super glue”)
- Fast-setting; available thin to thick, with accelerators.
- Great for small repairs, fixing chips, tacking parts, and filling tiny defects with sawdust.
- Not ideal for large joints or long-term structural loads.

7) Construction adhesives (hybrid)
- Not strictly “wood glue,” but often used for wood-to-nonwood (e.g., subfloors, trim to masonry).
- Thicker, gap-bridging, and flexible.

How to Choose the Right Wood Glue

Ask a few quick questions:
- Is the project interior or exterior? For outdoor, choose PVA meeting Type I/II, polyurethane, or epoxy.
- Do you need gap filling? Prefer polyurethane or epoxy; PVA wants tight joints.
- How much working time do you need? Extended-open-time PVA or epoxy provides more flexibility.
- Will you ever need to reverse the joint? Use hide glue.
- What materials are you bonding? For wood to non-wood, polyurethane or construction adhesive may be better.

Application Tips for Strong Joints

• Dry fit first: Assemble everything without glue to confirm alignment and clamp setup.
• Prep surfaces: Joint edges should be clean, flat, and freshly cut or sanded. Remove dust.
• Apply the right amount: Aim for a thin, even coat on both mating surfaces. A small, continuous bead that spreads to a light squeeze-out is ideal.
• Spread thoroughly: Use a brush, roller, glue spreader, or even a playing card to coat the entire surface.
• Clamp with even pressure: Use enough pressure to bring joints fully together without starving the joint. Pads or cauls help distribute pressure.
• Manage squeeze-out: Wipe PVA while it’s still wet with a barely damp cloth, or let it gel and scrape it off to avoid staining the wood.
• Watch temperature: Most PVAs prefer 55–75°F (13–24°C). Cold temps slow or prevent curing.
• Timing matters: Typical PVA clamp time is 30–60 minutes; handle gently after de-clamping and allow 24 hours for full cure. Epoxy and polyurethane times vary by brand and temperature.
• For polyurethane: Lightly mist one surface with water before gluing to activate cure; expect foam and mask off areas to ease cleanup.
• For epoxy: Measure accurately, mix thoroughly, and follow the manufacturer’s pot life and cure schedule.

Storage and Shelf Life

• PVA: Store above freezing; if it’s been frozen and turns lumpy or stringy, replace it. Shelf life is often 1–2 years unopened; test older glue on scrap.
• Keep caps clean: Wipe the nozzle, tap the bottle on the bench to settle glue away from the tip, and cap tightly.
• Epoxy and polyurethane: Seal well and store in a cool place; moisture and air shorten life. Keep hardener bottles clean to avoid contamination.

Common Mistakes to Avoid

• Using interior glue outdoors: Joints may fail with moisture and temperature swings.
• Expecting glue to fix loose joints: Glue needs contact; shim or remake parts so they fit before gluing.
• Over-clamping: Crushing all the glue out results in weak bonds.
• Rushing the cure: Don’t stress joints too soon. Even if clamps can come off, full strength takes longer.
• Poor surface prep: Oily woods benefit from a solvent wipe or light sanding just before gluing.
• Glue on finishing surfaces: Dried PVA can block stain. Locate and remove squeeze-out before finishing.
• Working too cold: Below the glue’s minimum temperature, curing may stall or fail.

Related Terms

• Open time: The workable window before the glue begins to set.
• Clamp time: Minimum time parts should stay clamped.
• Cure time: Time to reach full strength.
• Joinery: Methods for connecting wood parts (dowels, biscuits, mortise-and-tenon).
• Cauls: Straight boards used to spread clamping pressure.

Practical Examples

1) Edge-gluing a tabletop
- Joint and dry fit boards so edges meet tightly.
- Spread PVA evenly on both edges; assemble within the open time.
- Use clamps every 6–8 inches with light, even pressure. Check for flatness with winding sticks or a straightedge.
- Clean light squeeze-out; let cure overnight before planing or sanding.

2) Repairing a loose chair rung
- Disassemble carefully; scrape old glue from the mortise and tenon.
- Test fit. If the joint is sloppy, consider a shim or switch to epoxy.
- Apply glue, reassemble, and clamp with a strap clamp or cauls to protect round parts.
- Leave clamped per the glue’s instructions and avoid sitting on it for 24 hours.

3) Outdoor garden box
- Use a waterproof option (Type I PVA, polyurethane, or epoxy).
- Pre-drill and use exterior screws plus glue for extra strength.
- Seal exposed end grain well; it soaks up more glue.

4) Small chip repair on a cabinet corner
- Drip medium or thick CA into the chip, press the piece back, and use an accelerator if desired.
- Sand flush after it sets; touch up the finish.

With the right type of wood glue, good surface prep, and steady clamping, your projects can outlast the wood they’re made from.