If you watched the Shrek clip, you'll also recall that in that same scene, Lord Farquaad attempts to pull off one of Gingy's gumdrop buttons, which is where we get the sassy famous line, "Not the gumdrop button!" I thought maybe I'd use this as an introduction into the fzx behind adhesives. Like in band-aids, tape, glue...or gumdrops!

It doesn't sound very fzx-y at all...but when I was a kid I always wondered how when I made projects that I could glue something into place and it would slide around until it dried. What does letting these adhesives sit actually DO that make them stick?

Well according to my studies, (Dorothy Ann - The Magic School Bus), there are two types of forces that dictate the behavior of things that stick. There are cohesive forces as well as adhesive forces.

Examples? Water is created by hydrogen and oxygen naturally joining. That's a cohesive force. An adhesive force is like when a water droplet sticks to a glass window pane without any other type of glue, but with a different type of force.

The gumdrop clinging to Gingy would be of the adhesive type force. Under that there are a few sub-catagories as well:

Adsorption

This is glue without any chemical bonds. Just a load of tiny attractive forces caused by the spread out adhesive wetting the surface and forming numerous (and weak) electrostatic forces. These are called van der Waal forces after the physicist Johannes Diderik van der Waal who first discovered them.

Chemisorption

When glue is used on certain surfaces, like some plastics, it can sometimes actually form much stronger and tighter chemical bonds.

Mechanical

Adhesives can also work primarily physically without any sort of chemical attractions or bonds. For instance, when an object with holes in it is covered in glue, the glue seeps into it and grips the holes to connects the objects.

Diffusion

Finally, this is the theory that molecules from the two glued surfaces swap around and mingle together gluing the objects as one.

Gingy's gumdrops were probably glued on mechanically with frosting. In fact, I'm sure they were. So, while Lord Farquaad did almost pluck off his candy buttons, he didn't, because even with just a little adhesive, the purely physical bond was still fairly strong.

In the end, we can assume that Lord Farquaad may be small, but he certainly could rip a gumdrop off of a gingerbread cookie. But why didn't the gumdrop pop off right away? Well, as I have just explained, there's a simple scientific answer. And it could just save your life.

Or maybe only your gumdrop buttons.