Are bubbles science-y?

I’m sure we all remember the joy of blowing bubbles as kids. I think you were one of two types of kid: you either loved to watch them fly around for as long as the wind would hold them, or you loved to pop them and make the other type of kid sad. Those who know me will probably be pointing fingers at me as the second kind… Oops!

There is something about the way that bubbles drift in the breeze and catch the light…

A bubble glinting in the sunlight
A bubble drifting in the sunshine… Complete with Michael Bay lens flare.

but what about them is ‘science-y’? Well, I asked a bunch of roughly 10-year-old scouts what they thought and there was a split in opinions. Bubbles were either lame or amazing examples of ultra-thin materials.

Well, after researching thin films at water interfaces for four years, I can say that there is a lot of science to be found within the bubble and, fortunately, there is also a lot of fun too.

How to make bubbles behave

The film of the bubble is incredibly thin. So thin, in fact, that it interferes with the light trying to pass through and causes rainbow-like patterns in the bubbles (the same effect you might see when oil floats on water). This thin film makes them incredibly delicate! If anything punctures the layer of soap and water, the air trapped inside will rush out and the film of the rapidly-unbubbling-bubble will tear. The Slow Mo Guys have a great video showing the bubbles falling apart. If too much of the water in the film evaporates or pours down to the bottom of the bubble, it will pop too! 😦

So to make bubbles do your bidding, we need to either stop anything puncturing or damaging the soapy film or make the film stronger in the first place. To stop the bubbles puncturing, you can try to stop them touching a surface but, sooner or later, gravity, the wind or general universe mischief will have its way and pop your bubble. It is actually possible to get a bubble to sit nicely on a surface: the trick is to choose a surface that will trap a layer of air between the surface and the bubble.

PICT0043 (2).JPG
A bubble happily sat on a piece of foam.

We can also make bubbles stronger by adding things that can help to stabilise the soapy film. Soap is made up of molecules that are happy to interact with either water or oily stuff, so the bubble film will be stronger if something else can help the water and soap get along. Glycerol (often in the shops it is called glycerin, just one example of a chemical having about a billion different names) can mediate the water-soap interactions and make for stronger bubbles. You will need different amounts of glycerol in your bubble mix depending on what type of soap you are using (and what the water you are using is like – this will depend on where you are in the country and whether you have filtered the water at all), so you will have to experiment to find the best mixture.

glycerol.png
The structure of glycerol shown in two different ways.

What else can we do with bubbles?

Well, I’m planning to add some more experiments to this website as we go along but, in the meantime, if you want to see the amazing things you can do with bubbles, there are some true Bubble-Ninjas out there with incredible tricks and demonstrations to show you. Head over to Explorer Dome for more!

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