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Foam and the end of materiality

Sam Jacob digests the aerated structure of his Starbucks latte and Thatcherite ice cream

There is something unsettling about the stuff on top of a Starbucks latte. It sits, plumped and proud as a Teddy boy’s quiff, in a thoroughly unnatural way. It’s hard to believe that this voluminous, airy froth originated with anything as simple as milk. Only the faintly sour smell provides reassurance that it had something to do with a cow.

Steaming alters milk on a molecular level, breaking the milk’s chemical bonds, sweetening the taste by releasing lactose. Its texture changes as milk fat and water form an emulsion. The precise quality of the foam depends upon complex fluid dynamics: the speed, temperature and humidity of the steam, the nature of the nozzle, how the steam is introduced to the milk, the shape of the jug and the fat content of the milk.

The material’s architecture has changed. Matter is just on the right side of instability and collapse

The process of foaming multiplies surface area, increasing the sensation of taste. That’s partly why it’s become a staple in the avant-garde kitchens of molecular gastronomy. In the kitchens of the Fat Duck, chef Heston Blumenthal sprays his sour green-tea mousse into a spoon, then drops it into a bowl of liquid nitrogen to instantly freeze the foam into a glob of high-tech palate cleanser.

Just as it changes the nature of foodstuffs, foaming is used to alter a wide variety of materials. Applied to rubber, polystyrene, concrete, aluminium and glass, foaming or ‘aeration’ extends the original material’s qualities – making them lighter, stronger, more flexible, and giving them greater insulating properties.

During the manufacture of these kinds of substances, foam is created by inducing materials into a state of excitement. Once the foam has solidified, the material’s architecture has changed from solid to cellular in structure – a frozen ephemeral state, where matter is held just on the right side of instability and collapse.

Foam is semi-vanished, part ghostly

Foam adds complexity to materials. They become more ambiguous in their structure and behaviour. Where once materials gave grounding to the boundaries of human experience, these boundaries are hazy. Traditionally, we have regarded materials as a kind of ‘found’ truth inherited from nature – and thus fundamental and essential. Stone, for example, is characterised as an immovable foundation or a tablet of moral truth. Foam is substance that has become less physical, filled with miniature voids, expanded around and into air. It is semi-vanished, part ghostly.

We might consider Margaret Thatcher the patron saint of aeration. In the 1950s, Thatcher was part of a team of chemists working for food company J Lyons, investigating methods for preserving the foamy quality of ice cream. By experimenting with injecting air into ice cream until the point of collapse, they found that substituting vegetable oil for the animal fat naturally occurring within the dairy cream improved the emulsifying quality of the mix. The ‘improved’ ice cream could hold more air long enough for it to freeze. This frozen, swirled-up, foamy mixture of fat and sugar squirted out of machines as a premium product made with less substance.

It’s tempting to speculate on parallels between Thatcher’s chemical and political legacies

It’s tempting to speculate on parallels between Thatcher’s chemical and political legacies: perhaps Mr Whippy-esque ice cream represented a proto-privatisation of natural resource where air is transformed into commodity. One might even speculate that Thatcher’s chemical cue came from the Communist Manifesto, where Karl Marx describes capitalism’s transubstantive effect: ‘All that is solid melts into air.’ Perhaps Marx was staring at an ice cream as he struggled for the kind of linguistic imagery that would enthuse the proletariat.

Maybe the old modernists were right – there is a morality or even a politics to construction. Perhaps the rise of foam is a reflection of a more ambiguous political and moral era. A solid that reflects a condition described by the Buzzcocks’ Pete Shelly like this: ‘Hollow inside, we’re all hollow inside / But I couldn’t find out what the reason was / Why I was / Hollow inside.’ Maybe this is the existential scenario echoed in my Starbucks latte.

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