The Oxford Science Lecture Series

DR JACQUELINE AKHAVAN

Senior Lecturer in Chemisty, Cranfield University

"The Chemistry of Fireworks"

Inorganic Chemistry Laboratory, Oxford University 24th June 1998

Jackie Akhavan is a chemist specialising in explosives chemistry. Her research in the area of the chemistry of fireworks, which she has been doing for the last 10 years, is sponsored by Standard Fireworks. Her lecture, which was aimed a wide audience, sought to explain and demonstrate the properties of explosive materials which provide the sounds and colours which we experience at firework displays. This made for an exciting lecture full of noise, smoke and chemistry!

Jackie broke down the effects of fireworks into colour, noise and construction. She demonstrated how colour is achieved using different metal salts, and we experienced flashes of red, green and blue (which is the hardest to achieve it seems). She also explained how certain chemicals, in particular titanium, can be used to create the bright spark effects used, for example, in sparklers.

In looking at constructions of fireworks which can provide different effects, we were shown how the packing of the explosive material can alter the rate of burning, create noise and give different phases of the firework. These concepts were illustrated by Catherine wheels, fountains, roman candles and rockets. Believe it or not, two rockets were set off in the confines of the Inorganic Chemistry lecture theatre! This was achieved in safety by clamping the rockets firmly and pointing them downwards instead of up. We were asked to compare the sound produced by UK and Chinese-made bangers - both made everyone jump but the Chinese one was much louder. The feeling of the huge amount of energy being produced as each rocket exploded was perceptible in the lecture theatre.

Jackie finished by showing us some of the possible fireworks of the future which are being developed in her lab at the moment. These include a firework designed to have an effect like a strobe light, flashing on and off very rapidly as it burns out. The lab is also looking at safer contructions for the fireworks we already use, setting the explosive powders which have been used in the past into more stable polymer gels.

Safety was observed at all times during the lecture, with most fireworks (apart from sparklers) being set off behind a clear screen on the front desk. Jackie was careful to emphasise the potential dangers of explosives and the importance of observing the firework code. The audience, who ranged from young children to adults, all emerged from the lecture with a little smoke in their eyes but a better understanding of the chemistry which goes into producing fireworks.

Dr. Catherine Hobbs.