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In a shop you could be faced with an enormous choice of adhesives: some designed for specific tasks, others for joining more than one material.

In general there are six main types of adhesive:

• contact adhesive, of which the most familiar are Evo-stik and Thixofix
• woodworking adhesives - Unibond, for example
• cyanoacrylale adhesives or 'super glues'
• two-part epoxy adhesives Araldite is the most well known
• two-part acrylics, similar in usage to acrylics
• 'universal' or general-purpose adhe¬sives, such as U H U or Durofix.

As well as these main types, there are several specialist repair adhesives - for joining glass, for mending PVC and for joining polystyrene as well as adhesives for jobs such as fixing wall tiles, putting up wallcoverings and hobby work with paper and card.
When choosing an adhesive for a par¬ticular job, there are several points you need to think about.

First, what materials are you joining together? Obviously, the adhesive has to be suitable for both materials if they are different, but the main problem here is with plastics and recognising the plastic is the first task.

Second, how important is strength? With wood glues, the bond can be as strong as the wood itself, while with metal and plastics it will usually be weaker. If strength is all-important, you might need to think about reinforcing the joint in some way.

Third, how big a gap is there to fill? Often, joining two materials will also involve a degree of gap-filling, and adhesives vary in their ability to cope with this. Contact adhesives, for example, need a slight gap in which to work, while eyanoacrylates won't work unless the gap is very small indeed. Epoxy glues, on the other hand, will work with cither small or large gaps.

Fourth, what kind of temperature is the adhesive going to be subjected to? Some adhesives (known as thermoplastic), such as contact adhesives and many of the 'universal' glues, will not withstand heal, while many others (known as thermo¬setting) will retain their strength up to moderately high temperatures. This could matter when you are repairing crockery.

Finally, how important is the appear¬ance? Most adhesives dry to a clear finish, but some end up a pale creamy yellow. Whether or not this will show obviously depends on the thickness of the glue line and, equally importantly, how well you clear away the excess; with many glues, it is difficult to avoid some glue remaining.

Contact adhesives
The main uses for contact adhesives are for sticking thin coverings, such as plastic laminate and veneer, to a surface, and for shoe repairs.

A contact adhesive is applied to both the surfaces to be glued and left until it is dry. The two surfaces are then pressed together and the glue allowed to set. With most contact adhesives, the bond is made instantly (which means careful position¬ing); some contacts allow a short time during which the two surfaces can be adjusted.

Many contact adhesives are solvent based, which means good ventilation is important and that naked flames and cigarettes should not be allowed in the gluing area. Acetone (nail varnish remover) or a special remover is needed for a solvent-based contact adhesive; water-based contact adhesives can be removed with a damp cloth.

Glues for wood
The most common type of glue for wood¬working is the PVA (polyvinyl acetate) adhesive. Several brands are available and the recommended solvent is usually warm water.

Where the joint might get hot or be subjected to moisture, you should use one of the special thermosetting types often sold for outdoor use.

You can still get the traditional animal and fish glues used for woodworking: the main use of these is in furniture restor¬ation where it may be necessary at some point in the future to take the piece of furniture apart.

Cyanoacrylate adhesives
These so-called 'super glues' set almost instantly, provided there is just a small amount of moisture present. The adhesive is applied to one component and the other held against it for a few seconds. The two components need to fit almost exactly together for the glue to take.

Cyanoacrylates need care in use because they can bond skin together - finger to finger, finger to eyelid or eyelid to eyelid. Most manufacturers now make a special-release agent to cope with this - make sure you buy one unless it is provided as part of the pack.

Two-part epoxy adhesives
Although expensive to use for large glu¬ing jobs, epoxics are probably the most useful general repair type of adhesive. They are suitable for wood, metal, plastic and ceramic materials.

To use the adhesive, you mix the two parts (glue and hardener) together and apply the result to both surfaces. Setting times depend on temperature, but range from about five minutes up to thirty minutes or more. The result is both heat-resistant and unaffected by water. Use white spirit to remove excess adhesive.

Two-part acrylics
These are similar in usage to epoxics, but the method of use is different the glue is applied to one component and the hardener to the other.

They generally make stronger joints than epoxics (particularly on metal and plastics), but are not so resistant to wash¬ing and will not fill gaps as well. Use acetone to remove unset adhesive; dry glue can be removed with a trimming knife.

'Universal' adhesives
The main advantage of this type of adhesives is its case of use you just simply squeeze the adhesive out of a tube, smear it on the surfaces and allow it to set. However, the resultant joint will not be very good and should be used only where strength is not important.

Adhesives are very important. You should know how to choose the right adhesives from a long adhesive product list. Just buying something won’t help until you don’t know how to use adhesives.

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