Tin foil hat
A tin foil hat is a hat made from one or more sheets of aluminium foil, or a piece of conventional headgear lined with foil, worn in the belief or hope that it shields the brain from threats such as electromagnetic fields, mind control, mind reading. The notion of wearing homemade headgear for such protection has become a popular stereotype and byword for paranoia, persecutory delusions, belief in pseudoscience and conspiracy theories. "Tin foil" is a common misnomer for aluminium foil. An early allusion to an "insulative electrical contrivance encircling the head during thought" appears in the unusual 1909 non-fiction publication Atomic Consciousness by self-proclaimed "seer" John Palfrey who believed such headgear was not effective for his "retention of thoughts and ideas" against a supposed "telepathic impactive impingement"; the usage of a metal foil hat for protection against interference of the mind was mentioned in a science fiction short story by Julian Huxley, "The Tissue-Culture King", first published in 1926, in which the protagonist discovers that "caps of metal foil" can block the effects of telepathy.
Some people have a belief that such hats prevent mind control by governments, spies, or paranormal beings that employ ESP or the microwave auditory effect. People in many countries who believe they are "targeted individuals", subject to government spying or harassment, have developed websites, conference calls, support meetings to discuss their concerns, including the idea of protective headgear. Over time the term "tin foil hat" has become associated with conspiracy theories; the notion that a metal foil hat can reduce the intensity of incident radio frequency radiation on the wearer's brain has some scientific validity, as the effect of strong radio waves has been documented for quite some time. A well-constructed aluminum foil enclosure would approximate a Faraday cage for parts of the body enclosed by metal, reducing the amount of radio frequency electromagnetic radiation passing through to the parts of the body covered by the foil. Unlike a foil hat, a Faraday cage is a complete enclosure.
A foil hat does not protect the face, other uncovered areas of the body are not protected. A common high school physics demonstration involves placing an AM radio on aluminum foil, covering the radio with a metal bucket; the AM radio is 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 would be blocked, although aluminum foil is not sold in this thickness, so numerous layers of foil would be required to achieve this effect. A belief exists that aluminum foil is a protective measure against the effects of electromagnetic radiation for many unspecified EMR frequencies. Despite some allegations that EMR exposure has negative health consequences, no published experimental scientific evidence has established that tinfoil hats are effective.
In 1962, Allan H. Frey discovered that the microwave auditory effect can be blocked by a patch of wire mesh placed above the temporal lobe. Foil hats have appeared in novels, such as Signs and Futurama: Into the Wild Green Yonder. In Signs, the children and younger brother of the lead character wear tin-foil hats to prevent their minds from being read; the paranoid centaur Foaly, in Eoin Colfer's Artemis Fowl series of books, wears a tin-foil hat to protect from mind-readers. The novel Idiots in the Machine by Edward Savio portrays a character who believes tin foil keeps harmful gamma rays away, becoming a media sensation after marketing a successful line of foil hats to Chicago. Electromagnetic hypersensitivity Electromagnetic radiation and health Electronic harassment Electrophonic hearing Electrostatic discharge materials Embassy attack accusations in Cuba Faraday cage The Hum Microwave auditory effect On the Origin of the "Influencing Machine" in Schizophrenia Sonic weapon Media related to Tin foil hats at Wikimedia Commons
A chemical substance is a form of matter having constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e. without breaking chemical bonds. Chemical substances can be chemical compounds, or alloys. Chemical elements may not be included in the definition, depending on expert viewpoint. Chemical substances are called'pure' to set them apart from mixtures. A common example of a chemical substance is pure water. Other chemical substances encountered in pure form are diamond, table salt and refined sugar. However, in practice, no substance is pure, chemical purity is specified according to the intended use of the chemical. Chemical substances exist as solids, gases, or plasma, may change between these phases of matter with changes in temperature or pressure. Chemical substances may be converted to others by means of chemical reactions. Forms of energy, such as light and heat, are not matter, are thus not "substances" in this regard.
A chemical substance may well be defined as "any material with a definite chemical composition" in an introductory general chemistry textbook. According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. But, there are exceptions to this definition; the chemical substance index published by CAS includes several alloys of uncertain composition. Non-stoichiometric compounds are a special case that violates the law of constant composition, for them, it is sometimes difficult to draw the line between a mixture and a compound, as in the case of palladium hydride. Broader definitions of chemicals or chemical substances can be found, for example: "the term'chemical substance' means any organic or inorganic substance of a particular molecular identity, including – any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature". In geology, substances of uniform composition are called minerals, while physical mixtures of several minerals are defined as rocks.
Many minerals, mutually dissolve into solid solutions, such that a single rock is a uniform substance despite being a mixture in stoichiometric terms. Feldspars are a common example: anorthoclase is an alkali aluminum silicate, where the alkali metal is interchangeably either sodium or potassium. In law, "chemical substances" may include both pure substances and mixtures with a defined composition or manufacturing process. For example, the EU regulation REACH defines "monoconstituent substances", "multiconstituent substances" and "substances of unknown or variable composition"; the latter two consist of multiple chemical substances. For example, charcoal is an complex polymeric mixture that can be defined by its manufacturing process. Therefore, although the exact chemical identity is unknown, identification can be made to a sufficient accuracy; the CAS index includes mixtures. Polymers always appear as mixtures of molecules of multiple molar masses, each of which could be considered a separate chemical substance.
However, the polymer may be defined by a known precursor or reaction and the molar mass distribution. For example, polyethylene is a mixture of long chains of -CH2- repeating units, is sold in several molar mass distributions, LDPE, MDPE, HDPE and UHMWPE; the concept of a "chemical substance" became established in the late eighteenth century after work by the chemist Joseph Proust on the composition of some pure chemical compounds such as basic copper carbonate. He deduced; this is now known as the law of constant composition. With the advancement of methods for chemical synthesis in the realm of organic chemistry. However, there are some controversies regarding this definition because the large number of chemical substances reported in chemistry literature need to be indexed. Isomerism caused much consternation to early researchers, since isomers have the same composition, but differ in configuration of the atoms. For example, there was much speculation for the chemical identity of benzene, until the correct structure was described by Friedrich August Kekulé.
The idea of stereoisomerism – that atoms have rigid three-dimensional structure and can thus form isomers that differ only in their three-dimensional arrangement – was another crucial step in understanding the concept of distinct chemical substances. For example, tartaric acid has three distinct isomers, a pair of diastereomers with one diastereomer forming two enantiomers. An element is a chemical substance made up of a particular kind of atom and hence cannot be broken down or transformed by a chemical reaction into a different element, though it can be transmuted into another element through a nuclear reaction; this is so, beca
Phonograph cylinders are the earliest commercial medium for recording and reproducing sound. Known as "records" in their era of greatest popularity, these hollow cylindrical objects have an audio recording engraved on the outside surface, which can be reproduced when they are played on a mechanical cylinder phonograph. In the 1910s, the competing disc record system triumphed in the marketplace to become the dominant commercial audio medium. On July 18, 1877, Thomas Edison and his team invented the phonograph, his first successful recording and reproduction of intelligible sounds, achieved early in the following December, used a thin sheet of tin foil wrapped around a hand-cranked grooved metal cylinder. Tin foil was not a practical recording medium for either commercial or artistic purposes and the crude hand-cranked phonograph was only marketed as a novelty, to little or no profit. Edison moved on to developing a practical incandescent electric light and the next improvements to sound recording technology were made by others.
Following seven years of research and experimentation at their Volta Laboratory, Charles Sumner Tainter, Alexander Graham Bell and Chichester Bell introduced wax as the recording medium and engraving, rather than indenting, as the recording method. In 1887, their "Graphophone" system was being put to the test of practical use by official reporters of the US Congress, with commercial units being produced by the Dictaphone Corporation. After this system was demonstrated to Edison's representatives, Edison resumed work on the phonograph, he settled on a thicker all-wax cylinder, the surface of which could be shaved down for reuse. Both the Graphophone and Edison's "Perfected Phonograph" were commercialized in 1888. A patent-sharing agreement was signed and the wax-coated cardboard tubes were abandoned in favor of Edison's all-wax cylinders as an interchangeable standard format. Beginning in 1885, prerecorded wax cylinders were marketed; these have professionally made recordings of songs, instrumental music or humorous monologues in their grooves.
At first, the only customers for them were proprietors of nickel-in-the-slot machines—the first juke boxes—installed in arcades and taverns, but within a few years private owners of phonographs were buying them for home use. Each cylinder can be placed on and removed from the mandrel of the machine used to play them. Unlike shorter-playing high-speed cylinders, early cylinder recordings were cut at a speed of about 120 rpm and can play for as long as 3 minutes, they were made of a soft wax formulation and would wear out after they were played a few dozen times. The buyer could use a mechanism which left their surfaces shaved smooth so new recordings could be made on them. Cylinder machines of the late 1880s and the 1890s were sold with recording attachments; the ability to record as well as play back sound was an advantage of cylinder phonographs over the competition from cheaper disc record phonographs which began to be mass-marketed at the end of the 1890s, as the disc system machines can be used only to play back prerecorded sound.
In the earliest stages of phonograph manufacturing various competing incompatible types of cylinder recordings were made. A standard system was decided upon by Edison Records, Columbia Phonograph, other companies in the late 1880s; the standard cylinders are about 4 inches long, 2 1⁄4 inches in diameter, play about 2 minutes of music or other sound. Over the years the type of wax used in cylinders was improved and hardened so that cylinders could be played with good quality over 100 times. In 1902 Edison Records launched a line of improved hard wax cylinders marketed as "Edison Gold Molded Records"; the major development of this line of cylinders is that Edison had developed a process that allowed a mold to be made from a master cylinder which permitted the production of several hundred cylinders to be made from the mold. The process was labeled, "Gold Moulded" because of the gold vapor, given off by gold electrodes used in the process. All cylinders sold had to be recorded live on the softer brown wax which wore out in as few as twenty playings.
Cylinders were reproduced either mechanically or by linking phonographs together with rubber tubes. Although not satisfactory, the result was good enough to be sold. Cylinders were sold in cardboard tubes with cardboard caps on each end, the upper one a removable lid. Like cylindrical containers for hats, they were called "boxes", the word still used by experienced collectors. Within them, the earliest soft wax cylinders came swathed in a separate length of thick cotton batting. Molded hard-wax cylinders were sold in boxes with a cotton lining. Celluloid cylinders were sold in unlined boxes; these protective boxes were kept and used to house the cylinders after purchase. Their general appearance allowed bandleader John Philip Sousa to deride their contents as "canned music", an epithet he borrowed from Mark Twain, but that did not stop Sousa's band from profiting by recording on cylinders; the earliest cylinder boxes have a plain brown paper exterior, sometimes rubber-stamped with the company name.
By the late 1890s, record companies pasted a generic printed label around the outside of the box, sometimes with a penciled catalog number but no other indication of the identity of the recording inside. A slip of paper stating the title and performer was placed inside the box with the cylinder. At first this information was hand-written or typed on each slip, but printed versions became more common once cylinders were sold in large enough quantities to justify the printing set-up cost; the recording itself began with a spoken
World War II
World War II known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries; the major participants threw their entire economic and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China, it included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, the only use of nuclear weapons in war. Japan, which aimed to dominate Asia and the Pacific, was at war with China by 1937, though neither side had declared war on the other. World War II is said to have begun on 1 September 1939, with the invasion of Poland by Germany and subsequent declarations of war on Germany by France and the United Kingdom.
From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, formed the Axis alliance with Italy and Japan. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Finland and the Baltic states. Following the onset of campaigns in North Africa and East Africa, the fall of France in mid 1940, the war continued between the European Axis powers and the British Empire. War in the Balkans, the aerial Battle of Britain, the Blitz, the long Battle of the Atlantic followed. On 22 June 1941, the European Axis powers launched an invasion of the Soviet Union, opening the largest land theatre of war in history; this Eastern Front trapped most crucially the German Wehrmacht, into a war of attrition. In December 1941, Japan launched a surprise attack on the United States as well as European colonies in the Pacific. Following an immediate U. S. declaration of war against Japan, supported by one from Great Britain, the European Axis powers declared war on the U.
S. in solidarity with their Japanese ally. Rapid Japanese conquests over much of the Western Pacific ensued, perceived by many in Asia as liberation from Western dominance and resulting in the support of several armies from defeated territories; the Axis advance in the Pacific halted in 1942. Key setbacks in 1943, which included a series of German defeats on the Eastern Front, the Allied invasions of Sicily and Italy, Allied victories in the Pacific, cost the Axis its initiative and forced it into strategic retreat on all fronts. In 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained its territorial losses and turned toward Germany and its allies. During 1944 and 1945 the Japanese suffered major reverses in mainland Asia in Central China, South China and Burma, while the Allies crippled the Japanese Navy and captured key Western Pacific islands; the war in Europe concluded with an invasion of Germany by the Western Allies and the Soviet Union, culminating in the capture of Berlin by Soviet troops, the suicide of Adolf Hitler and the German unconditional surrender on 8 May 1945.
Following the Potsdam Declaration by the Allies on 26 July 1945 and the refusal of Japan to surrender under its terms, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki on 6 and 9 August respectively. With an invasion of the Japanese archipelago imminent, the possibility of additional atomic bombings, the Soviet entry into the war against Japan and its invasion of Manchuria, Japan announced its intention to surrender on 15 August 1945, cementing total victory in Asia for the Allies. Tribunals were set up by fiat by the Allies and war crimes trials were conducted in the wake of the war both against the Germans and the Japanese. World War II changed the political social structure of the globe; the United Nations was established to foster international co-operation and prevent future conflicts. The Soviet Union and United States emerged as rival superpowers, setting the stage for the nearly half-century long Cold War. In the wake of European devastation, the influence of its great powers waned, triggering the decolonisation of Africa and Asia.
Most countries whose industries had been damaged moved towards economic expansion. Political integration in Europe, emerged as an effort to end pre-war enmities and create a common identity; the start of the war in Europe is held to be 1 September 1939, beginning with the German invasion of Poland. The dates for the beginning of war in the Pacific include the start of the Second Sino-Japanese War on 7 July 1937, or the Japanese invasion of Manchuria on 19 September 1931. Others follow the British historian A. J. P. Taylor, who held that the Sino-Japanese War and war in Europe and its colonies occurred and the two wars merged in 1941; this article uses the conventional dating. Other starting dates sometimes used for World War II include the Italian invasion of Abyssinia on 3 October 1935; the British historian Antony Beevor views the beginning of World War II as the Battles of Khalkhin Gol fought between Japan and the fo
Tin is a chemical element with the symbol Sn and atomic number 50. It is a post-transition metal in group 14 of the periodic table of elements, it is obtained chiefly from the mineral cassiterite, which contains stannic oxide, SnO2. Tin shows a chemical similarity to both of its neighbors in group 14, germanium and lead, has two main oxidation states, +2 and the more stable +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest number of stable isotopes in the periodic table, thanks to its magic number of protons, it has two main allotropes: at room temperature, the stable allotrope is β-tin, a silvery-white, malleable metal, but at low temperatures it transforms into the less dense grey α-tin, which has the diamond cubic structure. Metallic tin does not oxidize in air; the first tin alloy used on a large scale was bronze, made of 1/8 tin and 7/8 copper, from as early as 3000 BC. After 600 BC, pure metallic tin was produced. Pewter, an alloy of 85–90% tin with the remainder consisting of copper and lead, was used for flatware from the Bronze Age until the 20th century.
In modern times, tin is used in many alloys, most notably tin/lead soft solders, which are 60% or more tin, in the manufacture of transparent, electrically conducting films of indium tin oxide in optoelectronic applications. Another large application for tin is corrosion-resistant tin plating of steel; because of the low toxicity of inorganic tin, tin-plated steel is used for food packaging as tin cans. However, some organotin compounds can be as toxic as cyanide. Tin is a soft, malleable and crystalline silvery-white metal; when a bar of tin is bent, a crackling sound known as the "tin cry" can be heard from the twinning of the crystals. Tin melts at low temperatures of about 232 °C, the lowest in group 14; the melting point is further lowered to 177.3 °C for 11 nm particles. Β-tin, stable at and above room temperature, is malleable. In contrast, α-tin, stable below 13.2 °C, is brittle. Α-tin has a diamond cubic crystal structure, similar to silicon or germanium. Α-tin has no metallic properties at all because its atoms form a covalent structure in which electrons cannot move freely.
It is a dull-gray powdery material with no common uses other than a few specialized semiconductor applications. These two allotropes, α-tin and β-tin, are more known as gray tin and white tin, respectively. Two more allotropes, γ and σ, exist at temperatures above 161 pressures above several GPa. In cold conditions, β-tin tends to transform spontaneously into α-tin, a phenomenon known as "tin pest". Although the α-β transformation temperature is nominally 13.2 °C, impurities lower the transition temperature well below 0 °C and, on the addition of antimony or bismuth, the transformation might not occur at all, increasing the durability of the tin. Commercial grades of tin resist transformation because of the inhibiting effect of the small amounts of bismuth, antimony and silver present as impurities. Alloying elements such as copper, bismuth and silver increase its hardness. Tin tends rather to form hard, brittle intermetallic phases, which are undesirable, it does not form wide solid solution ranges in other metals in general, few elements have appreciable solid solubility in tin.
Simple eutectic systems, occur with bismuth, lead and zinc. Tin was one of the first superconductors to be studied. Tin can be attacked by acids and alkalis. Tin can be polished and is used as a protective coat for other metals. A protective oxide layer prevents further oxidation, the same that forms on pewter and other tin alloys. Tin helps to accelerate the chemical reaction. Tin has ten stable isotopes, with atomic masses of 112, 114 through 120, 122 and 124, the greatest number of any element. Of these, the most abundant are 120Sn, 118Sn, 116Sn, while the least abundant is 115Sn; the isotopes with mass numbers have no nuclear spin, while those with odd have a spin of +1/2. Tin, with its three common isotopes 116Sn, 118Sn and 120Sn, is among the easiest elements to detect and analyze by NMR spectroscopy, its chemical shifts are referenced against SnMe4; this large number of stable isotopes is thought to be a direct result of the atomic number 50, a "magic number" in nuclear physics. Tin occurs in 29 unstable isotopes, encompassing all the remaining atomic masses from 99 to 137.
Apart from 126Sn, with a half-life of 230,000 years, all the radioisotopes have a half-life of less than a year. The radioactive 100Sn, discovered in 1994, 132Sn are one of the few nuclides with a "doubly magic" nucleus: despite being unstable, having lopsided proton–neutron ratios, they represent endpoints beyond which stability drops off rapidly. Another 30 metastable isomers have been characterized for isotopes between 111 and 131, the most stable being 121mSn with a half-life of 43.9 years. The relative differences in the abundances of tin's stable isotopes can be explained by their different modes of formation in stellar nucleosynthesis. 116Sn through 120Sn inclusive are formed in the s-process in most stars and hence they are the most common isotopes, while 122Sn and 124Sn are only formed in the r-process (rapid neutr
Aluminium foil referred to with the misnomer tin foil, is aluminium prepared in thin metal leaves with a thickness less than 0.2 mm. In the United States, foils are gauged in thousandths of an inch or mils. Standard household foil is 0.016 mm thick, heavy duty household foil is 0.024 mm. The foil is pliable, can be bent or wrapped around objects. Thin foils are fragile and are sometimes laminated to other materials such as plastics or paper to make them more useful. Aluminium foil supplanted tin foil in the mid 20th century. Annual production of aluminium foil was 800,000 tonnes in Europe and 600,000 tonnes in the U. S. in 2003. 75% of aluminium foil is used for packaging of foods and chemical products, 25% used for industrial applications. It can be recycled. In North America, aluminium foil is known as aluminum foil, it was popularised by the leading manufacturer in North America. In the United Kingdom and United States it is, informally called tin foil, for historical reasons. Metallised films are sometimes mistaken for aluminium foil, but are polymer films coated with a thin layer of aluminium.
In Australia, aluminium foil is called alfoil. Foil made from a thin leaf of tin was commercially available before its aluminium counterpart. Tin foil was marketed commercially from the late nineteenth into the early twentieth century; the term "tin foil" survives in the English language as a term for the newer aluminium foil. Tin foil is less malleable than aluminium foil and tends to give a slight tin taste to food wrapped in it. Tin foil has been supplanted by aluminium and other materials for wrapping food; the first audio recordings on phonograph cylinders were made on tin foil. Tin was first replaced by aluminium in 1910, when the first aluminium foil rolling plant, "Dr. Lauber, Neher & Cie." was opened in Emmishofen, Switzerland. The plant, owned by J. G. Neher & Sons, the aluminium manufacturers, started in 1886 in Schaffhausen, Switzerland, at the foot of the Rhine Falls, capturing the falls' energy to process aluminium. Neher's sons, together with Dr. Lauber, discovered the endless rolling process and the use of aluminium foil as a protective barrier in December 1907.
In 1911, Bern-based Tobler began wrapping its chocolate bars in aluminium foil, including the unique triangular chocolate bar, Toblerone. By 1912, aluminium foil was being used by Maggi to pack soups and stock cubes; the first use of foil in the United States was in 1913 for wrapping Life Savers, candy bars, gum. Processes evolved over time to include the use of print, lacquer and the embossing of the aluminium. Aluminium foil is produced by rolling sheet ingots cast from molten billet aluminium re-rolling on sheet and foil rolling mills to the desired thickness, or by continuously casting and cold rolling. To maintain a constant thickness in aluminium foil production, beta radiation is passed through the foil to a sensor on the other side. If the intensity becomes too high the rollers adjust, increasing the thickness. If the intensities become too low and the foil has become too thick, the rollers apply more pressure, causing the foil to be made thinner; the continuous casting method has become the preferred process.
For thicknesses below 0.025 mm, two layers are put together for the final pass and afterwards separated which produces foil with one bright side and one matte side. The two sides in contact with each other are matte and the exterior sides become bright; some lubrication is needed during the rolling stages. These lubricants are sprayed on the foil surface before passing through the mill rolls. Kerosene based lubricants are used, although oils approved for food contact must be used for foil intended for food packaging. Aluminium is annealed for most purposes; the rolls of foil are heated until the degree of softness is reached, which may be up to 340 °C for 12 hours. During this heating, the lubricating oils are burned off. Lubricant oils may not be burnt off for hard temper rolls, which can make subsequent coating or printing more difficult; the rolls of aluminium foil are slit on slitter rewinding machines into smaller rolls. Roll slitting and rewinding is an essential part of the finishing process.
Aluminium foils thicker than 25 μm are impermeable to water. Foils thinner than this become permeable due to minute pinholes caused by the production process. Aluminium foil has a matte side; the shiny side is produced. It is difficult to produce rollers with a gap fine enough to cope with the foil gauge, for the final pass, two sheets are rolled at the same time, doubling the thickness of the gauge at entry to the rollers; when the sheets are separated, the inside surface is dull, the outside surface is shiny. This difference in the finish has led to the perception that favouring a side has an effect when cooking. While many believe that the different properties keep heat out when wrapped with the shiny finish facing out, keep heat in with the shiny finish facin
A foil is a thin sheet of metal made by hammering or rolling. Foils are most made with malleable metals, such as aluminium, copper and gold. Foils bend under their own weight and can be torn easily; the more malleable a metal, the thinner foil can be made with it. For example, aluminium foil is about 1/1000 inch, whereas gold can be made into foil only a few atoms thick, called gold leaf. Thin foil is called metal leaf. Leaf tears easily and must be picked up with special brushes. Foil is used in household applications, it is useful in survival situations, because the reflective surface reduces the degree of hypothermia caused by thermal radiation. Aluminium foil Tin foil Gold leaf Metal leaf