We use adhesives in all kinds of ways. When an adhesive is spread over one side of a long, clear strip is is called adhesive tape (commonly known by the trade name Sellotape or Scotch tape). Adhesives can also be placed in tubes and squeezed out.

Flour, sugar, fish skins, bones and other animal products boiled in water all make adhesives, which is why adhesives have been known down the ages. The gums that drip from trees and leaves were used in the Stone Age.

An adhesive sticks to other materials, of course, but the tiny molecules that make up the adhesive also have to stick to one another.

Let's think of a natural sticky material like jam. If you put two slices together with jam inside you should be able to pick up the sandwich by just one of the slices. The jam is acting like a glue. But this is not a very good glue because the particles in the jam do not hold together very well. That is why it is just sticky, not a glue.

Notice that when you pull the slices apart, you are left with jam on both slices, so the jam is stuck to both. The jam glue has failed inside the jam. So making a good glue is simply a matter of making a material where the particles stick to one another as strongly as they do to the things they are sticking.

So what stops a glue sticking to the sides of the bottle or tube it is in? In many case it is because it is mixed with another substance that stops it being sticky. This could be as straightforward as water (say flour and water paste). When the glue is used, the water dries off and the glue sticks. So that kind of glue will not stick immediately. But if the glue is a substance that evaporates quickly – you will know this because you will be told not to breathe it in - then it will stick properly within seconds.

Did you know: paints have glues in them or they would not stick to surfaces.