Tin foil hat radio with a metal bucket. The AM radio is completely inside a metal enclosure. This leads to a noticeable reduction in signal strength received by the AM radio. The efficiency of a metal enclosure in blocking electromagnetic radiation depends on the thickness of the foil, as dictated by the "skin depth" of the conductor for a particular wave frequency range of the radiation. For half-millimetre-thick aluminum foil, radiation above about 20 kHz (i.e., including both AM and FM bands) would be partially blocked, although aluminum foil is not sold in this thickness, so numerous layers of foil would be required
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