Choosing adhesives and sealants: a handy guide

Most adhesives and sealants are quite specific in their usage and come in several varieties. So it's very important to make the right selection for the job at hand. Here's a handy guide to help you choose and use your adhesive or sealant.

• Frame sealants are used outdoors to fill gaps between frames and the surrounding masonry. Some can be painted over and some can be sanded.
• Silicone sealants are mainly used in bathrooms and kitchens to seal the join between the edges of fittings and countertops and walls.
• Roof and gutter sealant is either silicone or rubberized bitumen that's specially formulated for repairing gutters, downpipes, flat roofs and flashings.
• Decorator's sealant is a paintable gap-filler used indoors around doors, windows and ceilings, and along baseboards.

• White PVA adhesive (known widely as "wood glue") is perfectly all right for most indoor jobs.
• Polyaliphatic cross-linking PVA adhesive (better known as "yellow glue") is good for outdoor jobs. It's weather resistant and stronger than the standard stuff.
• Polyurethane adhesive is also worth considering. This adhesive is very strong and waterproof, so it's good for boat-building and outdoor furniture in very exposed conditions. But, polyurethane adhesive is more expensive than the PVA adhesives and is solvent based, so wear gloves when using it.
• Construction adhesive should not be overlooked. It's ideally suited for use on rough exterior joints.

1. Don't rely on clamps to pull together a poorly fitting joint. Adhesive and pressure may hold things together for a while, but in the long run the joint will fail. Make sure the pieces fit properly.
2. Before applying adhesive, test-fit the parts. Pre-adjust the clamps so they're ready to apply pressure with just a few twists.
3. Never force a clamp or use a spanner to tighten it. If the clamp isn't strong enough, use a bigger one or add another clamp next to it.
4. Too much clamping pressure can squeeze all the adhesive out of the joint and compress the timber. Too little pressure can result in a line of adhesive that is too thick and therefore weak. If a ridge of adhesive appears between clamped parts, stop applying pressure.
5. Leave the clamps on for the recommended length of time.
6. A broken hacksaw blade spreads adhesive quickly over a large, flat area. The teeth let the adhesive flow easily and keep it to a smooth, even overall depth.
7. As any model-maker knows, toothpicks are perfect for applying glue in tight areas with precise control.

Consider this handy guide when you're choosing your adhesives and sealants and you'll be better able to make the right selection for the job at hand.