People went to extraordinary lengths, in the days before electricity, to make frozen puddings. The first bit, admittedly, is a little tricky: you have to wait until winter, find a frozen lake, cut huge chunks of ice out of it and bury them in an underground cavern. (This is not to make the ice cream in, it’s just to ensure a plentiful supply of ice in the summer.) Cover the cavern well with insulating material (sticks, straw etc).
Assuming you now have ice to hand, the interesting bit follows.
A quick trawl of my kitchen produced a salt cellar, a few ice cubes, skimmed milk, saucepan & small tin pot.
I poured the milk into the small tin, put it in the saucepan, and arranged the ice cubes around it. There wasn’t many ice cubes, only half a tray’s worth. They only came a third of the way up the tin and looked very much as if there ought to be more of them. I poured some sea salt liberally on top.
I have to say, it didn’t look good. The saucepan sat there, with its oddly pathetic and enormously unappetizing contents. It looked both unscientific and unlikely to yield any form of treat, frozen or otherwise. After some thought — it was a warm summer’s day — I put the saucepan lid on.
. . . One hour later, I took the lid off and looked inside. The ice was mostly still there and the milk appeared to be unchanged.
I got a cup of room-temperature milk, to help see if there would be any difference between it and the milk in the tin, but I didn’t believe there would be any. Or if there was, naturally the milk in the tin would be slightly cooler, perhaps, just because of having been closer to the ice.
I lifted the tin, took a swig — and received a mouthful of ice-cold liquid saturated with delicate, frangible, and unmistakeable flakes and shards of frozen milk.
It was wonderful, I felt like an alchemist. The frozen milk melted in my mouth exactly as ice cream does, the initial punch of coldness making the ensuing flavour of milk a delightful surprise. This was not slightly cooled milk, it was well on its way to ice cream.
I’m off to find a lake and wait for a bit. Will keep you posted on the next experiment.