STICKING POINT

In this extract from her new book Sticky: the secret science of surfaces, NZ resident Laurie Winkless examines the origin of Post-it Notes and superglue, and finds out why lotus leaves are so damn slippery.

- Laurie Winkless

How can we know if we have a good adhesive or not? Well, “good” is a relative term. Water might be able to stick a coaster on to the bottom of a glass, but you wouldn’t want to rely on it to hold a plate together. And if sticky tape instantly created a permanent bond, wrapping birthday gifts would become a high-stakes activity.

When choosing an adhesive, we’re mainly looking for a material that’s able to resist the forces that will act on it during its lifetime. Exactly what those forces look like will vary hugely depending on our specific needs. And vitally, there’s no way to separate out an adhesive’s behaviour from that of the surfaces it’s sticking to. What that means in real terms is that everything depends on everything else. This is why there is no simple, objective measure of stickiness; no single number that will encapsulate all that you need to know about a product. The best we can do with commercial adhesives is to design tests that reflect how those products will be used in the real world.

There are a lot of adhesive products on the market, as well as a huge number of measurement standards and recognised test set-ups that put them through their paces.

So rather than try (and fail) to go through everything, I’ve picked out the two products that I think everyone is familiar with.