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) or fastening a knob on the point ("blossom", French "fleuret"). In addition to practising, some fencers took away the protection and used the sharp foil for duels. German students took up that practice in academic fencing and developed the "Pariser" ("Parisian") thrusting small sword for the "Stoßmensur" ("thrusting mensur"). The target area for modern foil is said to come from a time when fencing was practised with limited safety equipment. Another factor in the target area is that foil rules are derived from a period when dueling to the death was the norm. Hence, the favoured target area is the