It is hard to imagine a chemical reaction more thrilling than spontaneous combustion. One example of this phenomenon occurs when two common chemicals come together: swimming pool chlorine and brake fluid.

Swimming pool chlorine and brake fluid are household chemicals that are often found in a garage or shed. When you combine these chemicals, you create an improvised explosive consisting of an oxidizing agent – calcium hypochlorite, which is swimming pool chlorine – and a fuel source, polyethylene glycol-based brake fluid. When the fuel rapidly oxidizes in the presence of the oxidizing agent, the mixture spontaneously combusts, resulting in a fireball.

Because this experiment involves mixing volatile compounds and produces a fireball, it is dangerous. The only safe way to conduct this experiment is to use very small quantities of the ingredients in a laboratory with a fume hood while under the supervision of an expert. Anyone present during the experiment should wear a face shield.

Place 2 to 2.5 grams of swimming pool chlorine, in an open evaporating dish under a fume hood. Pipette 1 milliliter of brake fluid into the evaporating dish. Step away from the fume hood to observe the experiment from a safe distance.

After combining the ingredients, you should expect a short period of dormancy. Nothing will happen for between 5 and 30 seconds, depending on the freshness of the swimming pool chlorine. It is important not to approach the fume hood during this time even if you suspect the experiment did not work.

You should hear a hiss in the evaporating dish followed by a fireball within a second of the sound. This fireball should flare and die quickly and is likely to shatter the evaporating dish.

Mixing swimming pool chlorine with brake fluid is an exciting experiment that displays the power of oxidation. When performed under safe circumstances, it is a thrilling introduction to combustion in the chemistry laboratory.