Making ice-cream
This method replicates the oldest method available for making ice cream. All methods depend on the fact that salt lowers the freezing point of ice so by adding more ice and salt, one can produce a brine solution much colder than 0 deg C and this in turn removes heat from the ice cream mixture in the metal pan allowing it to cool and freeze.
You will need:
For the volcano shape:
- A large plastic bowl or washing tub
- A metal container – like a metal cooking pot – the thinner the better
- Ice
- Salt
- Water
- 600 ml milk
- 80g fine sugar
- 400 ml double cream
- Flavourings – whatever you like – cocoa powder, liquidised strawberries, etc.
- An alcohol thermometer for low temperature reading if you can get one.
And last but not least ... a helping hand from an adult.
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Method
First you must put the sugar, milk and cream into the thin metal pot and beat well.
Next put the metal pot into the outer container (a plastic container would work best, ideally this should be not much bigger than the pot).
Add ice cubes (which will start to melt) and the salt and some water.
Stir the ice cream mixture, adding the flavour of your choice. Keep adding salt and ice to the outer basin. The coldest you can get is with 20% salt in the water solution (this means 200 g of salt for every litre of water). More than this is wasted.
Keep stirring till the cream begins to thicken and harden – then call in your friends and family and serve them some home-made ice-cream- science style.