Aluminium foil with all metallic items, aluminium foil reacts to being placed in a microwave oven. This is because of the electromagnetic fields of the microwaves inducing electric currents in the foil and high potentials at the sharp points of the foil sheet; if the potential is sufficiently high, it will cause electric arcing to areas with lower potential, even to the air surrounding the sheet. Modern microwave ovens have been designed to prevent damage to the cavity magnetron tube from microwave energy reflection, and aluminium packages designed for microwave heating are available. Heavier foils made of aluminium are used for art,
Foil (fencing) Olympics, although some organizations still fence competitively with non-electric swords. Foil have standardized, tapered, quadrangular (rectangular) blades that are made of tempered and annealed, low-carbon steel—or maraging steel as required for international competitions—and are designed to bend upon striking an opponent in order to prevent both injuries and breakage of the blade. The foil blade is no more than 90 cm in length with a blunted (or "foiled") tip, the maximum length of the assembled weapon is 110 cm, and the maximum weight is 500g; however, most competition foil are lighter, closer to 350g. The blade itself is subdivided into