As useless as a chocolate teapot: part 1

07 April 2015

Interview with

Dave Ansell and Ben Valsler, Naked Scientists

How often have you heard the saying "as useless as a chocolate teapot?" The teapotProbably quite often. But is it really useless? We dispatched Naked Scientists Ben Valsler and Dave Ansell to find out...

Ben - Why is it that a chocolate teapot would be so useless?

Dave - Well the reason why chocolate is so nice to eat is that it's the point at which it melts is very similar to the temperature of your mouth. So, it should melt in your mouth. So, as you're going to put boiling water into it, it should melt really quickly and just collapse.

Ben - So, I guess what we need to find out is how thick the walls of the chocolate teapot need to be in order to not melt through by the time the tea is brewed. How are we going to find this out?

Dave - We could just make lots of chocolate teapots but that will take ages and use a really ridiculous amount of chocolate. So instead, what I've got is a whole series of tubes with different amounts of chocolate in the bottom of each one and then pour boiling water over them and see how long they take to melt.

Ben - So, the tubes aren't actually sealed at the bottom. There's just a plug of chocolate in there of different thicknesses. In theory, at least one of these thicknesses of chocolate should stay solid long enough to brew a cup of tea.

Dave - Well, because I've got no idea how thick this has got to be, I've gone from very wide range of different thickness of chocolate from about 10 mm up to about 80 mm. So, one of those ought to survive the brewing time.

Ben - It looks to me like you've chosen to go for dark chocolate.

Dave - Milk chocolate's got a lot of milk fat in it and milk fats got lower melting temperature than coco fat. So, dark chocolate ought to melt at high temperatures. So, it would be slightly better than milk chocolate for these purposes.

Ben - Okay, so I guess the first thing we need to do in that case is boil a kettle and pour some water into each of these tubes.

Dave - I'll go and get that kettle.

Ben - So, while Dave goes to get the kettle, I'm just going to have a look at these tubes of chocolate and they are just plastic tubes open at both ends with a thick plug of chocolate. I don't think these are going to last very long when we pour boiling water in. here comes Dave now with a steaming hot kettle so we can try it out. So Dave, are you going to put them in any particular order?

Dave - Well, I figured I'd start on the thickest plug of chocolate first because that should last the longest. So, it's probably the fairest to start with that one. I'll try and put that same amount of water on top of each one roughly so it's a fair test.

Ben - So, there isn't a different weight of water that could just push the plug of chocolate out.

Dave - Yeah, that's the idea.

Ben - So, what else is in chocolate? I know you've already mentioned coco fats and milk fats but surely, there's more to it than that.

Dave - Well, a good quality dark chocolate is basically just coco fat, some coco solid which are the things which aren't fat from a coco bean and lots of sugar.

Ben - Okay, well there's just been a bit of activity with these tubes. The tube with the thinnest plug of chocolate in has just dropped some chocolate onto the floor and emptied itself. In fact, that's really not a very pleasant thing to watch the way it's just oozing chocolate into a dollop on the floor. Dave, how long did that take?

Dave - That seems to have been about 4 minutes which is not bad for only a 10-mm piece of chocolate. It's a lot better than you'd expect really.

Ben - And 4 minutes is actually about as long as you need to brew a cup of tea.

Dave - Indeed. So, maybe chocolate is a better teapot material than we'd first thought.

Ben - So now that we know that a thickness of chocolate which is only about 10 mil or so, about a centimetre, should be thick enough to make a teapot out of. Shall we make a teapot?

Dave - Yeah, I think so. We'll probably make one with rather thicker walls than that because a teapot is quite a lot bigger than the 40-mm tubes we're using. So maybe we'll go for about 20-mm wall and see what happens.

Ben - Excellent! And I do like my tea quite strong so it will be good to be able to brew it for that a little bit longer. So, Dave and I are now going to go into his kitchen and make ourselves a chocolate teapot. We'll come back to you later on the show to let you know how good it was at brewing some tea.

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