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 opal Foil opal Foil opals are simulated opal gemstones that first came into vogue during the jewelry-making boom of the late-Victorian era. Across Europe and the United States, these faux gemstones joined their paste counterparts (simulated diamonds, emeralds, rubies and sapphires made from glass) as the need for jewelry outstripped both gemstone availability and nouveau middle-class budgets. The term 'foil' refers to an actual metal foil that was sometimes used to create reflection and sparkle behind milky glass or quartz faces. Though technically incorrect, other simulated opals with various types of sparkling inclusions or shiny backings are sometimes also referred to