John Hart — Thermette

John Hart invented a simple device that boils 12 cups of water using a few twigs in five minutes flat. This invention, the Thermette, became treasured equipment for soldiers in the Second World War and is still today virtually unchanged.

Able to boil 12 cups of water in five minutes using only a few twigs and sticks is one New Zealand invention which has served its users in all weather and conditions without a hitch for over 60 years. The invention is the Thermette or Benghasi Boiler.

It was first invented in 1929 by John Ashley Hart but became a cultural icon and found its true home and place in New Zealand's history during the Second World War. For New Zealand soldiers fighting the deserts of North Africa the Thermette became a standard and treasured piece of equipment and earned the nickname the `Benghasi Boiler'.

NZ dictionary says the Benghasi Boiler got its name from the town of Benghazi in Libya, presumably a town near where the New Zealanders were based at some time early on during the war in the North African desert. Its inventor John Hart started working for A & T Burt as an electrical goods salesman around the Manawatu region after the First World War but left this job to form his own business in Auckland, J A Hart Co, in the 1920s. His business produced electrical equipment but Mr Hart's real love was invention.

The Thermette was just one, and the most successful, of 32 different inventions he patented during his life. It has a simple and highly efficient design. Basically it consists of a cone shaped chimney which runs through a water jacket. It stands about half a metre high and can be fuelled with anything, from sticks and newspaper to gas or kerosene.

The tapered chimney causes the air and smoke to rise quickly, creating an area of low pressure which rapidly draws in air to fuel the flames and create a lot of heat energy. This combines with the large surface area of the cone shaped chimney to transfer the heat to the water very quickly.

Mr Hart patented and named his Thermette in 1931 and began making them in blue, green and orange tin or the more expensive tinned copper. The Thermette caught on and came with the guarantee to boil up water for 12 cups of tea in five minutes in any weather with any fuel or your money back.

It was originally advertised with the slogan `the more the wind the quicker it boils', indicating its usefulness in bad weather when other stoves might not work. However it was not until World War Two that the Thermette's useful and clever design really earned its keep.

The story goes that John Hart had sold one of his Thermettes to an army sergeant sometime before the war who told his superior officers just how great it was and suggested it could be useful to the army.

When war broke out in 1939 the army came to Mr Hart and asked him to waive the patent so they could make their own Thermettes. He agreed and the `fastest water boiler around' was issued as standard equipment to every small army unit.

The sites where the New Zealanders set up camp were always marked by circles of scorched earth where the Benghasi Boiler had been used for a brew up. Enemy troops overtaking positions previously held by the allies were reported to be puzzled by the marks until they learnt to identify them with the New Zealanders and their unique water boiler.

John Hart is now dead but his Thermette is still boiling water around the country and even on the other side of the world. Thermettes are now sold and marketed in Auckland by Kestrel Developments and has hardly changed in design since John Hart first built his original Thermette.

Director of Kestrel Developments Trevor Tull is proud to be associated with the Thermette and it fits nicely alongside some other examples of kiwi ingenuity which his company is involved with including a non-toxic paint stripper made from plant acids.

Mr Tull had one letter sent to him from a family in the south of England expressing their thanks to the Thermette after a severe storm with 170 km/h winds which cut power to their house.

Cornwall man James Barlow wrote to Mr Tull to tell him what a great thing the Thermette was and how one a friend in Southland had given him came in mighty handy during that storm.

"We were without power for four days and we didn't know which way to turn until I remembered the Thermette. It was simplicity itself to use even in the garage where I had to take shelter from the awful weather, what a wonderful invention. It was used everyday during the power failure and certainly saved us from hypothermia."

The simplicity and usefulness of the Thermette looks likely to see it being used by campers, picnickers, trout fishers, outside workers and countless others well into the next millenium.

Not bad for a modest, old New Zealand invention.

Classroom activity - Conduction & Convection