Flame’n Elements

Flame Tests with Group 1 Alkali Metals


I recently shot a short series of flame test films demonstrating the different coloured flames produced when burning group 1 alkali metals. The films were shot at the Royal Institution and produced for the Royal Society of Chemistry’s Learn Chemistry site.

Here’s what happens when you burn Caesium salts:

Metal salts were disolved into a methanol solution (the fuel) and this was soaked into the wireframe structures of the element symbols (Rb = Rubidium, Cs = Caesium etc.) – these were then lit to produce some really beautiful flame colours, ranging from red (Lithium) to blue (Caesium). Each element has its own unique colour or spectrum – almost like a signature colour which is directly related to its chemical properties.

Rubidium has a sort of red-violet colour:

By burning the metal ions, we’re exciting electrons causing them to move into higher energy states. These are fairly unstable states to be in so the electrons eventually move back down into lower energy states and as they do this they emit light. The wavelength and resulting spectra of light given off during this process are specific to each element (giving a range of pretty colours!) and can be used to identify different metals from one another. If you have a spectroscope (an instrument that essentially lets you look at the make-up of light) you can see the individual spectra given off by the flames.

The RSC has published some learning materials around these videos which will give you a much clearer idea of the chemistry at hand if you’re interested.

Aside from shooting pretty flames, these films also gave me opportunity to play about with titles and compositing – using the flame footage as flickering colour fills for the Element names.

I really like this effect and hope to experiment with it further in future films.

The flame test demonstrations were originally featured in the 2012 Christmas Lectures – which you can view here (around 30 mins in).


Christmas Lectures 2012 – Behind the Scenes

The Modern Alchemist

One of the great pleasures of working at the Royal Institution is witnessing the frenzy that goes on behind the scenes in the lead up to the Christmas Lectures. This year the lectures cover the chemical elements and are presented by Dr Peter Wothers, a fellow of the Royal Society of Chemistry and teaching fellow at the University of Cambridge.

The beautiful reaction seen between Caesium and Fluorine
The beautiful reaction seen between Caesium and Fluorine

The lectures themselves are available for a limited period on iPlayer, but will also be available to stream indefinitely on the Ri Channel, the team behind them have done an incredible job and so they’re well worth a watch – you don’t necessarily need any scientific background or knowledge of Chemistry to enjoy them!

Naturally this year’s subject lends itself well to the presentation of scientific demonstrations and there has been plenty of opportunity for loud bangs and fire spewing explosions. However, the lectures have also provided chance to perform some very rare and unusual demonstrations – and it’s these that have formed the subject of a couple of behind the scenes films produced for the Ri Channel:

Reacting Caesium and Fluorine (First time on camera)

Fluorine and Caesium are the two most reactive elements in the periodic table and so for the lectures, Peter was very interested in trying to react them both together. However their extreme reactivity also means that they’re both very dangerous to work wit, so it was important Peter found the right person to work with! Enter Dr Eric Hope a Fluorine specialist at the University of Leicester and so on a grey day in November we travelled up to see how this reaction might work and I think it might be the first time it has ever been caught on camera!

What was particularly nice about this meeting was that Peter had never previously seen Fluorine and Eric had never seen Caesium! This demo features in the second lecture, ‘Water: The Fountain of Youth’.

Cloud Chamber

I was so pleased I got to see this demo with my own eyes, I’d previously heard a lot about cloud chambers and seen a few bits of ropey footage on the internet, but never actually seen one in the flesh (so to speak). It’s essentially a particle detector with a sealed environment that is supersaturated with alcohol vapour and as charged particles zip through the vapour they ionize it, allowing condensation trails to form.

It’s an absolutely beautiful thing to look at, as it makes visible the background radiation that exists all around us and on the last day of recording I was lucky enough to capture this close-up on camera:

This demonstration features in the third lecture entitled ‘The Philosopher’s Stone’.

Testing Hydrogen Balloons

Lastly, the Christmas Lectures wouldn’t be complete without some sort of gratuitous explosion and so here’s a little film about testing different sized hydrogen balloons: