Kitchen Physics

The Baked Alaska is an experiment that is certainly worth doing at home. The idea is that you place a block of icecream on a sponge base, and then smother it in meringue (for those who have only ever bought a pavlova, that means well beaten (stiff) egg white, with sugar folded in, about 50 grammes per egg-white). Stuff the whole thing into a hot oven (about 230 degrees, I think) for about 3 minutes or so, and, if all goes to plan, you should have a nice meringue crust with a soft, cold, ice-cream centre.

This works because of the very low thermal conductivity of the meringue. The beaten egg-white contains lots of tiny air bubbles, which hinder the flow of heat through it – in effect making a goodinsulating blanket around the ice-cream.  So when we put it in a hot oven, for a short space of time, the effect is only to cook the outermost bit (equals nice meringue) leaving the frozen inside almost untouched. 

If you have enough people to help you clean up the evidence afterwards, experiment with different cooking times and oven temperatures. For example, if the oven’s too cold, you’ll need a longer cooking time to get the meringue nice, but that gives time for the heat to get through to the ice-cream.  

Many years ago I saw on TV a physicist (can’t remember who) make a reverse Baked Alaska (maybe a Baked Antarctica?)  Here, you start with the ice-cream, drill out about a 5 cm diameter cylindrical cavity inside it, and stuff the cavity with the meringue. Then you place a thick electrical wire through the cavity, pass a lot of current through it, and the heat starts cooking the meringue from the inside.

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