Star Turn: Peter Barham

Microwaving balloons? It must be a lecture on polymer physics. David Mosford talks to an embarrassment-proof lecturer who loves penguins.

Peter Barham believes there is more to life than polymer physics. Things such as cooking (his hobby) and penguins (his passion). His Bristol University office is littered with them - cuddly penguins, penguin screensavers and, of course, Barham's waistcoat, a natty number bought for him by his wife, Barbara, herself a penguin activist.

Barham spends as much time as he can observing penguins in their natural habitat. He even has his undergraduate students testing polymers to find out what kind of tagging band can survive the Antarctic cold without fitting so tightly that circulation is cut off. But his main interest is polymer physics: "Understanding how long molecules rearrange themselves when changing from liquid to solid state and vice versa," Barham explains.

"If you take a plastic bag and heat it, the molecules move from looking like stalks of spaghetti lined up in rods to looking like a plate of spaghetti (as it melts). It happens in an instant."

Cookery is a prevalent metaphor for Barham. His introductory lecture to first-years involves boiling water in a paper bag. The paper does not burn - much to the surprise of most students - because the water impregnates the paper, and as water boils well below the point that paper burns, the bag full of water will boil without the paper being affected.

It is the kind of demonstration that has students rushing back to their halls of residence to show that physics can be fun after all.

Peter Barham has also been known to put a balloon full of water in a microwave to demonstrate the expansion of liquids when heated and to cook potatoes in class to demonstrate thermal diffusivity. "What determines the time it takes to boil a potato is diameter. A potato cooks at 60C. By cutting through it, you can observe by the change of texture how far it has cooked in a certain period of time."

Barham took up cookery as a hobby after completing his PhD at Bristol and has found it an invaluable teaching aid. He has also written his own cookery book, The Science of Cooking (Springer), which takes well-known recipes back to their physical and chemical first principles.

Having been at Bristol for 28 years, Barham has no qualms about his occasional stunts in the lecture theatre. "Comic asides can be what helps students remember," he says.

"There's an axiom that the standard lecture goes from the blackboard to the students' notes bypassing the brains of both lecturer and student, but if you provide spectacular demonstrations or are willing to make a bit of a fool of yourself, things get remembered."

Barham has not always been such a star turn. "When I started lecturing, I was terrified of undergraduates because I was sure they all knew more than me. But now that I've come to realise that they don't know that they know more than me, I've become embarrassment-proof."