Aluminised Plastic Film Puff (square)

Part mirror, part pillow, and entirely delightful, this shiny, floaty ravioli traps air in between two sheets of metallised plastic film. It and its larger siblings in our window display were made by Katie Hammond, the Materials Library’s Creative Lead. 

To make one of these puffs, you would follow this recipe. Find two sheets of aluminised plastic film with a heat-sensitive adhesive layer. Overlay them so that their shiny sides are out. Use a clothes iron to bring the temperature of the edges higher than 150°C, binding the two adhesive layers together and creating an air-tight seal. Pump air into the space in the middle and inflate the puff until it has reached its proper plumpness, then seal the area you poked the air nozzle into with a final dab of heat. 

As this making process unfolds, you’d experience a symphony of futuristic sounds: from a shrill hiss as the air flows past the initially flat sheets, to the slow, low-frequency ‘whoop’ sounds of the inflation phase, before ending with a surprising cacophony of sparkling crackles as the balloon becomes bloated. The spectacle would also extend into the visual realm. You’d first see the uninflated sheets as a somewhat dull and flat mirror. As air is pumped and the puff comes alive as a three-dimensional object, you’d see its surface become shinier and more reflective, and its shape become a bulging, distorting mirror. At the end, when the balloon packs in more air than it would care to take in, you’d marvel at its edges becoming covered in smaller and smaller undulations. 

These wrinkles are the large-scale signature of a microscopic tug-of-war happening inside the plastic film. The internal air pressure inside the ballon expands the plastic film, pulling it tight in all directions. If you pull on a rubber band, it becomes thinner: materials under tension usually react by thinning out. But the edges of our puffs are sealed shut, so the plastic sheets cannot shrink their surface. Instead, they can squeeze into a smaller volume by creating ripples. The beautiful regularity of these wrinkles speaks to artists, who value their aesthetic qualities, and to material scientists, who can tell from their size and number how stiff the plastic membrane is and how much air pressure the puff is under. 

Over a hundred of these aluminised plastic film puffs were made for our first Materials Library window display celebrating aluminium. In the installation, two opposing versions of aluminium contrast and echo one another in two big masses: a dark, matte, angular giant ball of crumpled cinefoil in the middle of a shiny, airy, bouncy sea of puffs.