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,
Cold foil printing spools from an unwind and is nipped to a substrate. Foil sticks to the tacky adhesive on the substrate, and an image with a bright foil surface is created. Foil that does not adhere to the adhesive remains on a thin polyester liner, and waste is directed to a rewind spool. Because the adhesive is applied on press like a conventional ink, no expensive stamping die has to be created. Once printed, the surface of cold foil images may be varnished, laminated, or encapsulated in order to provide a hard-wearing, durable surface. Some printing substrates are unsuitable for cold foil