Thermette

What makes the Thermette brilliant is that it is perfect. In the 85 years since it was invented, no improvements have been made on it. It has been manufactured under the same patent continuously for that whole time and it remains, as it was, the quickest, most efficient way to boil water in the outdoors.

The inventor’s name was John Ashley Hart (b. 1887, d. 1964) and he was originally, like many great things, from the Manawatu. Most of Hart’s 32 other patents are now forgotten, but the Thermette, invented in 1929, caught on as standard equipment for New Zealand troops during World War II. The army approached Hart to ask if he would waive the patent to help in the war effort, and he agreed. The small round scorch marks it left on the earth at first confused the German troops all over North Africa, where the Thermette gained its army nickname, the ‘Benghazi Boiler’. Soon everyone knew the scorch marks were a sure sign that Kiwis had been there.

The Thermette can boil enough water for 12 cups of tea in just five minutes, using any old rubbish as fuel. ‘The stronger the wind, the better it boils,’ was one of Hart’s early slogans, because wind sucks air up through the conical chimney inside the boiler from the base where the fire is lit. The sucking action makes the fire roar, and the heat is transferred not only to the base of the Thermette, but through the heated air rushing up the internal chimney. No heat is wasted, and that is why the Thermette is so efficient. Its efficiency makes it an environmentally sound product, and it uses no pollutant gas, petrochemicals or hydrocarbons.

The original Thermette was first sold in 1931 in a blue, green and orange tin, or in tinned copper if you had a few extra bob. MS Services Ltd in Auckland is still making them to the same design. It used to be that any council workers, postal workers, and telegraph men on the side of the road could be seen setting up their Thermette, but they have largely disappeared from our roadsides. At the height of their popularity tens of thousands were made a year; now it is just a few thousand, but Trevor Tull at MS Services is hopeful for a resurgence in popularity. They are still proudly manufactured in New Zealand – the Thermette name and brand is very much a Kiwi tradition.

Even the army is still using them – in fact the Thermette used to have an official UN equipment number. They aren’t as widespread as they once were, because some modern armed vehicles (e.g. the New Zealand Army’s light armoured vehicles or LAVs) have built-in water heaters, but the Armoured Corps used to routinely have one or two Thermettes in each vehicle. Boiling a Thermette used to be a great social event, attracting all the other military personnel in the area for a cuppa. Solders would fill a cut-down shell case with petrol and drop a match in to light it – about a cup will be enough to boil a standard-issue Thermette. However, this method did cause problems, particularly when it was necessary to boil several in a row – the unwary trooper filling a hot shell case for the first time might not notice the remnants of the previous fuel still boiling and consequently would be engulfed in flames as the vapour ignited. This looked particularly spectacular early in the morning or late in the evening when the air was still, but as Brigadier Sean Trengrove, director general of the Army Reserves, remembers it, the only injuries were to pride and eyebrows. The cuppa escaped unscathed.

Among other fans of the Thermette we can number Sam Neill, Kiwi actor, who remembers it from his youth in Central Otago. ‘I learned how to stay downwind of the aromatic manuka-fuelled Thermette to avoid the sandflies.’

The Thermette is a modest but brilliant invention, still given regularly as gifts and used fondly on family picnics, although driftwood is recommended as fuel, rather than the petrol method the army used! It’s a brilliant piece of engineering – one of our real gifts to the world. Put the Thermette on and have a cuppa.