Crumpled Cinefoil Ball

The enormous, crumpled, light-devouring asteroid in our window display, and its tiny sibling in your hand, are both made from cinefoil or blackwrap foil. This lightweight, rigid but malleable aluminium foil is thicker than kitchen foil so that it keeps its shape when you sculpt it, but is soft enough to be crumpled by hand, cut to size with scissors, and stapled together. 
 
Photographers and film and theatre lighting technicians use this material to modify or create specific lighting equipment with excellent names like snoots, gobos, barndoors, eggcrates and flags. In this process, they repeatedly bend, angle and sculpt this thin sheet to get their desired lighting effects. Cinefoil therefore needs to be both malleable and formable. These properties describe the slightly different ways in which aluminium can be deformed without cracking or breaking: it can be compressed by flattening, hammering or rolling and can be shaped in multiple directions at once without breaking. 

In the grand scheme of materials, all metals are relatively malleable, formable and ductile. The extent to which metals can be deformed depends on their crystal structure. At the microscopic level, metals are made up of lots of tiny crystals, called grains, which are tessellated together in a pattern that looks a bit like crazy paving. When you casually bend a paperclip or push a chunk of aluminium through an industrial hydraulic press, you are forcing these tiny grains to stretch, bend, and slide past one another. 

These tiny grains are composed of trillions of billions of atoms all packed together in different patterns, and interrupting these regular patterns are dark squiggly lines called dislocations. These dislocations are imperfections in the atomic structure of the metal crystal that are very useful to us because they can move within the crystal, allowing little bits of material to slide from one side of the grain to the other so it can change shape, deform, and slide past its neighbours.

Different metals are more or less strong, brittle or ductile because of how easy or hard it is for these dislocations to move. This is partly affected by how tightly and regularly packed and how strongly bonded the atoms inside their crystals are, as this affects how easily dislocations can slip around inside the crystal. Aluminium is better at deforming than, say, tungsten because its atoms are more closely packed together but less strongly attracted to each other. Perhaps counterintuitively, this closely packed structure allows dislocations to glide and slip around inside aluminium’s crystals with relative ease, without fracturing the bonds between atoms. Tungsten’s atoms are less closely packed but more strongly attracted, making tungsten strong but brittle. Neither metal is as malleable as lead though, whose dislocations move so easily that you can bend thick pieces by hand, dent it with your fingernail, and roofers can cut it with a knife.

Unlike our reflective multi-layer insulation film and aluminised plastic film puffs, this sheet is coated in a matte black paint that absorbs nearly all light, making it super useful in photography for controlling, channelling and blocking all glare and unwanted reflections that could wash out an image. Because traditional tungsten or halogen photography and theatre lights can get extremely hot, this material is particularly suited to its purpose. Aluminium is among the most thermally conductive metals (coming in just behind silver, copper and gold) and it dissipates heat very quickly, rapidly moving it away from its source and dumping it out into the environment. The blacker the material, the more heat it radiates away too (see our super black for more on this). Although this foil can get scorchingly hot when attached to high powered lighting equipment, it cools down very quickly once they are turned off.