There are many different fuels that may be burned: gas in Bunsen burners, butane in gas lighters, alcohol in spirit burners, kerosene in common cook stoves, refined heavy oil (used by caterers) in metal cups, wax in candles, and charcoal in clay or metal stoves. Fire has three uses in the school laboratory – heating solutions, heating solid samples, and flame tests – so it is good to know which you are trying to do.

The ideal heat source has a high heat rate (Joules transferred per second), little smoke, and cheap fuel. A charcoal stove satisfies all of these but takes time to light and requires relatively frequent re-fuelling. Kerosene stoves have excellent heat rates but are smoky. Alcohol infused refined heavy oil burns smokeless and the heat rate scales with the size of the container – filling the bottom half of a cut off aluminum can will produce significant heat per unit time. In some countries this fuel is advertised for home and commercial use (e.g. Motopoa brand in Tanzania) and use is easy to find. In other countries, it might be much less common. 29

The ideal heat source has a high temperature and no smoke. Ideal would be be a Bunsen burner. For heating small objects for a short time (no more than 10-20 seconds), a butane lighter provides a very high temperature. Refined heavy oil will provide a flame of satisfactory temperature for as long as necessary.

The ideal heat source has a high temperature and produces a non-luminous flame. The Bunsen burner is ideal. The next best flame is again refined heavy oil – hot and non-luminous. Spirit burners produce a non-luminous flame at much greater cost, unless methylated spirits are used as fuel in which case the flame is much cooler. A butane lighter produces a very hot flame of sufficient size and time for flame tests although the non-luminous region is small. Kerosene stoves will work for some salts, especially if you pull the wicks longer or remove the outer protective shell (usually green) to give students access to the hotter blue flame in between the inner shells. As can be seen by the above discussion, alcohol infused heavy oil burners provide the best compromise heat source. They are also the easiest of these heat sources to use – pour the fluid into an open-topped metal container and set it on fire. They are also the safest heat source – they produce no smoke (unlike kerosene and candles), do not have fuel that spreads when it spills (kerosene and ethanol), nor can explode like gas. Students do not have to hold the burning apparatus (as with a lighter) and the flame may be extinguished by simply blowing it out or smothering it with a lid. Finally, the burners themselves are free – soda bottle tops, medicine and liquor bottle caps, cut aluminum cans, and metal tins; different sizes for different size flames. If you have access to this fuel, we strongly recommend using it. No matter which heat sources you use, always have available fire-fighting equipment that you know how to use. See item 5 in Specific Guidelines to Reduce Risk for more about fires. Remember that to put out a Bunsen burner safely, you need to turn off the gas.