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
Foil stamping Foil stamping Foil stamping, (also known as foil application) typically a commercial printing process, is the application of metallic or pigmented foil on to a solid surface by application of a heated die onto foil, making it permanently adhere to the surface below leaving the design of the die. In the process known as hot foil stamping, foil stamping machines uses heat to transfer metallic foil to a solid surface. Examples of items that are foil stamped include annual reports, pocket folders, product packaging, note cards/thank you cards, business cards, envelopes and letterhead. The foil stamp is a permanent process.