The Complete Adhesive Buying Guide

Why Glues Fail

Most failed repairs come down to the wrong glue, poor surface preparation or the wrong expectations about strength, not a bad product. Every adhesive works by wetting the surfaces, filling microscopic texture and then hardening, either by drying, by reacting with moisture, by reacting between two mixed parts or by cooling. If the glue cannot wet the surface, cannot fill the gap or is too rigid or too weak for the forces on the joint, it will fail.

The most common causes of failure are:

• Wrong adhesive for the materials. Super glue on a flexible rubber strap, wood glue on metal, or almost any glue on polyethylene.
• Dirty or oily surfaces. Fingerprints, dust, mould release agents on plastics, and old glue residue all block a bond.
• Smooth, glossy surfaces. Most glues grip better on a lightly roughened surface.
• Gaps the glue cannot fill. Super glue and wood glue need close contact; epoxy and construction adhesives fill gaps.
• Too little clamping, or too much. Joints need firm contact but should not be squeezed dry.
• Stressing the joint before full cure. Handling strength can arrive in minutes; full strength often takes 24 hours or more.
• Peel forces. Most adhesives are much stronger in shear, where surfaces slide past each other, than in peel, where one edge is lifted away. Design joints to avoid peeling where possible.

The Main Types of Adhesive

PVA wood glue

Yellow and white PVA glues are the standard for woodworking. On a well-fitted joint, the bond is often stronger than the surrounding wood. They need porous surfaces, firm clamping for 30 minutes to an hour and a day for full strength. Type I and Type II rated wood glues add water resistance for outdoor furniture and cutting boards. Our list of the best wood glue covers standard and specialist options, and our lists of the best waterproof, exterior and fast-drying wood glues cover specific needs.

Cyanoacrylate super glue

Super glue cures in seconds when it meets the trace moisture on surfaces. It is ideal for small, tight repairs on rigid materials such as ceramics, hard plastics, metal, wood trim and models. Gel versions are easier to control and fill slightly larger gaps; thin versions wick into hairline cracks. Rubber-toughened super glues resist shock better than standard formulas. Super glue is brittle and weak in peel, so it is a poor choice for flexible items or joints that take impacts. Our list of the best super glue, our reviews of Gorilla Super Glue Gel and Loctite super glue, and our comparison of the two cover the main options.

Two-part epoxy

Epoxy is the most versatile structural adhesive at home. You mix equal parts resin and hardener, apply and clamp lightly. Five-minute epoxies are convenient for small repairs; slower-setting 30-minute or overnight epoxies are stronger and give time to align parts. Epoxy fills gaps, bonds unlike materials such as metal to wood, and many formulas are waterproof once cured. Steel-filled epoxies and epoxy putties rebuild missing material. Our lists of the best epoxy glue for wood and the best glue for metals cover epoxy options.

Polyurethane glue

Polyurethane glue cures with moisture and expands as it does, filling gaps and producing foam squeeze-out. It is waterproof and bonds wood, stone, metal, ceramics and some plastics. Lightly dampen one surface before applying, clamp firmly to control foaming, and trim squeeze-out once cured. Wear gloves; it stains skin for days.

Construction adhesive

Construction adhesives come in caulk tubes and are designed for big jobs: subfloors, panelling, trim, stair treads, landscape blocks and foam board. They are strong and gap filling but slow to cure and not suitable for fine work. Choose a formula that matches the materials, for example a foam-safe formula for polystyrene insulation board. Our guide to the best glue for wood to concrete covers this territory.

Contact cement

Contact cement is applied to both surfaces, left to become tacky, and then pressed together, bonding instantly. It is the choice for laminate on countertops, leather, rubber, cork and veneers. There is no repositioning once surfaces touch, so alignment must be right first time. Solvent-based versions have strong fumes; water-based versions are safer indoors. Our list of the best adhesive for rubber to rubber covers flexible bonding.

Which Glue for Which Materials

Our job-specific roundups cover the trickiest pairings in more detail, including the best glue for plastic on plastic, the best waterproof adhesive for plastic, the best glue for glass to glass and the best glue for metals.

Glue vs Tape vs Fasteners

Glue is not always the right answer. Mounting tapes, mechanical fasteners and adhesives each suit different jobs.

• Double-sided mounting tapes, especially acrylic foam tapes, bond instantly, spread load over a large area and tolerate some flex and temperature change. They are excellent for mounting trim, mirrors designed for tape, hooks, signs and car badges to smooth, clean surfaces. They are weaker on rough or porous surfaces and can fail with constant heavy loads.
• Removable adhesive strips hang light pictures and hooks without damaging paint. Follow the weight rating and the removal instructions.
• Screws, nails, bolts and rivets hold immediately, can be undone and carry heavy loads, but they need holes and can split materials.
• Adhesives spread loads evenly across the whole joint, seal against water, bond thin or delicate materials and leave no visible fixings, but they take time to cure and are usually permanent.

Many of the strongest joints combine both. Woodworkers glue and screw cabinet backs; builders glue and nail subfloors to stop squeaks; car makers bond and rivet panels. If a joint will carry significant weight, or failure would be dangerous, use mechanical fasteners as well as adhesive.

Wood Glue in Depth

Wood glue deserves extra detail because it is the most widely used adhesive in homes and workshops.

• White PVA glue is general purpose, dries clear and suits interior crafts and furniture.
• Yellow PVA, sometimes called aliphatic resin or carpenter's glue, grabs faster, sands better and is the standard for interior woodworking.
• Type II water-resistant glue suits outdoor furniture, planters and kitchen items that get wet occasionally.
• Type I waterproof glue handles harsher exposure and has a longer open time for complex glue-ups.
• Hide glue, liquid or hot, is reversible with heat and moisture, which makes it the choice for antique restoration and musical instruments.
• Polyurethane and epoxy are better choices than PVA for oily tropical woods, end grain that needs gap filling and joints between wood and other materials.

Apply PVA to both surfaces for maximum strength on large joints, spread it thinly and evenly, and clamp until squeeze-out turns rubbery. End grain absorbs glue quickly; pre-coat it with a thin layer, let it soak in for a few minutes, then apply more glue before assembly.

Understanding Plastics

Plastic is the material where glue choice matters most, because different plastics behave very differently. Look for a recycling code or material marking moulded into the part.

• ABS, PVC, acrylic and polystyrene are relatively easy to bond with plastic cements, solvent welds, epoxy and super glue.
• Polycarbonate bonds with specialist adhesives and some epoxies, but solvent-based cements can cause crazing.
• Polyethylene (codes 2 and 4) and polypropylene (code 5) are low surface energy plastics. Almost nothing sticks to them without a primer or a specialist adhesive. Food containers, outdoor furniture, bins and many car parts are made from these.
• Nylon, silicone and PTFE are also very hard to bond.

If you do not know the plastic, test the adhesive on a hidden area first. A quick check: if a strip of masking tape barely sticks to the surface, it is likely a low surface energy plastic that needs a specialist adhesive.

Surface Preparation

Preparation decides most bonds.

1. Clean. Remove dust, grease and oil with isopropyl alcohol or a degreaser. Avoid acetone on plastics, which can dissolve them. For wood, a dry brush or vacuum is usually enough.
2. Roughen. Lightly sand glossy surfaces with medium grit sandpaper to give the glue something to grip. On metal, sand to bright metal and clean again.
3. Dry. Most glues need dry surfaces. Polyurethane and super glue need trace moisture, which is usually present already; polyurethane benefits from lightly dampening one surface.
4. Fit. Check the parts fit together before applying glue, and plan how you will clamp them.
5. Remove old glue. Old adhesive prevents new glue reaching the material. Scrape, sand or soften it before re-gluing.

Clamping, Working Time and Cure Time

• Open or working time is how long you have to position parts after applying glue. Super glue gives seconds; slow epoxies give 30 minutes or more.
• Clamp time is how long the joint needs pressure before it can be handled.
• Full cure is when the adhesive reaches its rated strength, often 24 hours, sometimes longer in cold conditions.

Use enough pressure to bring surfaces into firm contact and produce a small bead of squeeze-out, but not so much that the joint is starved of glue. Spring clamps, bar clamps, painter's tape, rubber bands and weights all work depending on the job. Cold temperatures slow almost every adhesive; most cure best above about 15°C (60°F).

Waterproof and Weatherproof Ratings

Waterproof claims vary. For wood glue, the ANSI/HPVA standard gives the most useful labels: Type II passes a water resistance test suitable for outdoor furniture that is not submerged, and Type I passes a more demanding boil test for harsher exposure. Neither is designed for permanent submersion; for boats and below-waterline work, marine epoxy is the standard. For other adhesives, check the product description for waterproof, weatherproof, UV resistance and temperature range, and whether it is safe for potable water or food contact if that matters.

Strength Ratings and What They Mean

Adhesive packaging often lists strength in psi or MPa, usually for tensile or lap shear strength. These numbers are measured under ideal lab conditions on specific materials, and higher numbers do not always mean a better joint at home. A brittle super glue with a high number can still snap when dropped, while a lower-rated flexible adhesive survives. Choose by material, gap, flexibility and environment first, and use strength figures only to compare products of the same type.

Common Household Repairs and the Glue to Use

Working With Two-part Epoxy

Epoxy is easy to get right if you follow a few rules.

1. Measure carefully. Most consumer epoxies are mixed one to one by volume. Twin syringes dispense equal amounts automatically; squeeze them gently and evenly.
2. Mix thoroughly. Stir on a disposable surface for the full time on the label, often 30 to 60 seconds, scraping the sides. Streaks of unmixed resin never cure properly.
3. Respect the working time. A five-minute epoxy begins to thicken within a few minutes of mixing. Mix only what you can use, and apply it promptly.
4. Use light pressure. Clamp only enough to hold the parts; squeezing too hard forces epoxy out of the joint.
5. Wait for full cure. Handling strength arrives within the set time, but full strength often takes 24 hours.
6. Clean up before it cures. Wipe excess with a paper towel and isopropyl alcohol while wet. Cured epoxy can only be sanded or cut away.

Slow-curing epoxies are generally stronger and more heat resistant than five-minute versions, so use the slowest product your patience allows for important repairs.

Removing Glue

Sometimes you need to undo a repair or clean up squeeze-out.

• PVA wood glue softens with warm water and heat; scrape squeeze-out once it is rubbery, before it hardens fully. Dried glue blocks stain, so remove it before finishing.
• Super glue softens with acetone on surfaces that tolerate it, such as glass, metal and skin. Test on plastics first, because acetone damages many of them.
• Epoxy softens with heat from a heat gun or hair dryer, which can allow joints to be separated. Cured epoxy residue usually needs sanding or scraping.
• Construction adhesive and polyurethane are best removed mechanically once cured, with a scraper, oscillating tool or sander.
• Hot glue releases with a little isopropyl alcohol at the edge of the bond on smooth surfaces.
• Adhesive residue from tapes and labels responds to citrus-based removers, oil or isopropyl alcohol.

Common Mistakes

• Using an all-purpose glue for everything. No glue is best at every job.
• Applying too much glue. Thick glue lines are weaker for most adhesives; a thin, complete layer is stronger. Epoxy and construction adhesives are the exception where gaps exist.
• Gluing over paint, varnish or old glue. The bond is only as strong as the layer underneath.
• Skipping clamping or moving the joint too soon.
• Gluing in the cold. Most adhesives cure slowly or poorly below about 10 to 15°C.
• Expecting glue to replace mechanical fasteners. For heavy loads, add screws, dowels or stitching.
• Using super glue on items that flex, take impacts or get hot.

Safety

• Ventilate. Solvent-based adhesives, contact cements and some construction adhesives release strong fumes. Work outdoors or with windows open, and read the label.
• Protect skin and eyes. Wear nitrile gloves with epoxy and polyurethane, and eye protection with super glue and anything that may splash.
• Super glue on skin. Do not pull bonded skin apart. Soak in warm soapy water and gently roll or peel; acetone-based nail polish remover helps on unbroken skin. Seek medical help if glue gets in your eyes.
• Food contact. Most adhesives are not food safe. For items that touch food, use a product explicitly rated for food contact once cured.
• Children and pets. Store adhesives out of reach, and keep fast-setting glues away from children.
• Disposal. Let leftover two-part products cure before disposal, and follow local rules for solvent-based products.

Storage and Shelf Life

Adhesives have shelf lives that shorten once opened.

• Keep super glue cool and dry with the cap tight. Some people store unopened tubes in the fridge; let them reach room temperature before opening to avoid condensation.
• Wipe nozzles before closing tubes to prevent clogging.
• PVA wood glue must not freeze; frozen glue can become lumpy and weak.
• Polyurethane glue cures in the bottle once exposed to moist air; squeeze out air before capping.
• Two-part epoxy lasts well if the parts are kept separate and sealed.

If a glue has thickened, separated or changed colour, replace it. A cheap new tube costs less than a failed repair.

What to Keep in a Home Glue Kit

Add hot glue if you do crafts. With those in a drawer, most household repairs are covered.

Budgets

Adhesives are cheap compared to the cost of a failed repair, and price differences between good brands are small. Paying a little more for a specialist product that suits the job is almost always worth it. Value packs of small single-use tubes are better than one large tube for super glue, which tends to harden once opened. For large projects, buying construction adhesive by the case or wood glue by the gallon cuts the cost significantly.

How We Recommend Shopping

1. Identify both materials, including the type of plastic if relevant.
2. Decide whether the joint is tight or has gaps.
3. Consider flexibility, impact, heat, water and UV exposure.
4. Choose the adhesive family from the chart above.
5. Pick a product in that family with the working time and cure time you need.
6. Prepare surfaces properly and clamp the joint.

Then start with our main list of the best adhesives for the job you have.

Every adhesive guide on BuyOnceRight

This guide is the hub for our adhesive coverage. Each page below answers one specific question in more depth.