question: How can you stick your entire hand into an open flame[camp fire, lighter] for a few seconds with minimal damage, but touching a hot metal [stove] burns instantly?
comment: Air is a poor thermal conductor, but a great insulator. In other words, air is greedy. Once gets heat it wants to hold onto it and doesn’t like giving it away. Metal on the other hand is a great thermal conductor. But a poor insulator. Metal likes to share heat with anything that wants some, like your hand. Metal gets a gold star in kindergarten for sharing its heat, while air gets a time out for hogging the heat for itself.
passages: Section::::Remote welding.
  
  "Remote exothermic welding" is a type of exothermic welding process for joining two electrical conductors from a distance. The process reduces the inherent risks associated with exothermic welding and is used in installations that require a welding operator to permanently join conductors from a safe distance from the superheated copper alloy.
  
  The process incorporates either an igniter for use with standard graphite molds or a consumable sealed drop-in weld metal cartridge, semi-permanent graphite crucible mold, and an ignition source that tethers to the cartridge with a cable that provides the safe remote ignition.
  
  Section::::See also.
  
  BULLET::::- Rail lengths
   Humphry Davy discovered the use of platinum in catalysis. In which a catalytic body is interposed in the path of a combustible vapor and is heated upon its passage through the catalytic body sufficiently to unite with the air upon egress from the catalytic body and then to burn upon the surface of the catalytic body. These stoves are typically described as wind-resistant, infrared, or radiant.
  
  BULLET::::- Rechauds Catalytiques (1920, wicking)
  
  BULLET::::- Therm'x Explorer 57C (1965, wicking)
  
  BULLET::::- MSR Reactor (2007, pressurized)
  
  BULLET::::- Rechaud A Catalytise Trek 270 (2010, pressurized)
  
  Section::::Pressurized liquid fuel stoves.
  
  Section::::Pressurized liquid fuel stoves.:Primus stoves.
   BULLET::::- At Thomas Edison's laboratory, an agent of the Goldschmidt Chemische-Thermo Industrie of Essen, Germany, demonstrated a process to melt iron in five seconds. "Louis Dreyfus of Frankfort-on-Main ... showed Mr. Edison his new process for attaining an enormous degree of heat in an incredibly short period of time by the combustion of a certain chemical compound which the inventor keeps a secret," the New York "Times" reported, "then placed a six-inch long iron wrench in a crucible and created a fire that reached 3,000 degrees centigrade."
   BULLET::::- Open flames. This varies from a lit cigarette to welding activity.
  
  BULLET::::- Mechanically generated impact sparks. For example, a hammer blow on a rusty steel surface compared to a hammer blow on a flint stone. The speed and impact angle (between surface and hammer) are important; a 90 degree blow on a surface is relatively harmless.
   The amount of heat applied to the metal is a function of the welding tip size, the speed of travel, and the welding position. The flame size is determined by the welding tip size. The proper tip size is determined by the metal thickness and the joint design.
   BULLET::::- Foreign objects in the embers may result in burns. Metal is especially dangerous since it has a high thermal conductivity.
  
  BULLET::::- Embers which have not burned long enough can burn feet more quickly. Embers contain water, which increases their heat capacity as well as their thermal conductivity. The water must be evaporated already when the firewalk starts.
  
  BULLET::::- Wet feet can cause embers to cling to them, increasing the exposure time.
   For a burn to be classified as electrical, electricity must be the direct cause. For example, burning a finger on a hot electric steam iron would be thermal, not electrical. According to Joule's first law: electricity passing through resistance creates heat, so there is no current entering the body in this type of burn. Likewise, a fire that is ruled to be "electrical" in origin, does not necessarily mean that any injuries or deaths are due to electrical burns. Unless someone was injured at the exact moment that the fire began, it is unlikely that any "electrical" burns would occur.
   BULLET::::- 7 April – At Thomas Edison's laboratory, an agent of the Goldschmidt Chemische-Thermo Industrie of Essen, Germany, demonstrated a process to melt iron in five seconds. "Louis Dreyfus of Frankfort-on-Main...showed Mr. Edison his new process for attaining an enormous degree of heat in an incredibly short space of time by the combustion of a certain chemical compound which the inventor keeps a secret," the New York "Times" reported, "then placed a six-inch long iron wrench in a crucible and created a fire that reached 3,000 degrees centigrade."
   BULLET::::- An antique cast iron cookstove is a simple iron box on legs, with a cast iron top. A wood or coal fire is built inside the box and food is cooked on the top outer surface of the box, like a griddle. If a fire is built too hot, and then the stove is cooled by pouring water on the top surface, it will crack due to thermal shock.
   Metals can burn under the right conditions, similar to the combustion process of wood or gasoline. In fact, rust is the result of oxidation of steel or iron at very slow rates. A thermite reaction is a process in which the correct mixture of metallic fuels combine and ignite. Ignition itself requires extremely high temperatures.
   Metallic objects in contact with the skin may "concentrate" the lightning's energy, given it is a better natural conductor and the preferred pathway, resulting in more serious injuries, such as burns from molten or evaporating metal. At least two cases have been reported where a strike victim wearing an iPod suffered more serious injuries as a result.
   Arc welding uses a low voltage and high current electric arc between an electrode and the base material to melt the metals at the welding point, which often creates sparks. To reduce the risk of burns, welders wear heavy leather gloves and long sleeve jackets to avoid exposure to extreme heat, flames, and sparks. In spot welding, metal surfaces that are held in contact are joined by the heat from resistance to electric current flow. It is common for a spray of sparks in the form of molten metal droplets to be ejected from the parts being joined. or the resistance heating of spot welding.
   Section::::Methods.:Friction.
  
  Fire can be created through friction by rapidly grinding pieces of solid combustible material (such as wood) against each other (or a hard surface) which are heated and create an ember. Successfully creating fire by friction involves skill, fitness, knowledge, and acceptable environmental conditions. Some techniques involve crafting a system of interlocking pieces that give the practitioner an improved mechanical advantage; these techniques require more skill and knowledge but less fitness, and work in less ideal conditions. Once hot enough, the ember is introduced to the tinder, more oxygen is added by blowing and the result is ignition.
   The melting point of iron is . When blacksmiths heat the iron up to Celsius, the solid iron will melt and turn into liquid iron. The splash of heated liquid iron is an energy transformation process. The potential energy of the surface of liquid iron transforms to kinetic energy when the blacksmith throws out the iron from the furnace. The explosion of molten iron is essentially an oxidation reaction.  When the blacksmith flings the molten iron against the wall, the carbon impurity in the iron will react with oxygen to produce carbon dioxide and the impact between the carbon in the iron and the cold wall will react and produce sparks. With the same performance process, the higher the carbon amount of the iron, the more sparks can be formed.
   BULLET::::- Water has a very high specific heat capacity (4.184 J g K), whereas embers have a very low one. Therefore, the foot's temperature tends to change less than the coal's.
  
  BULLET::::- Water also has a high thermal conductivity, and on top of that, the rich blood flow in the foot will carry away the heat and spread it. On the other hand, embers have a poor thermal conductivity, so the hotter body consists only of the parts of the embers which are close to the foot.
   Section::::Explanation.
  
  When two bodies of different temperatures meet, the hotter body will cool off, and the cooler body will heat up, until they are separated or until they meet at a temperature in between. What that temperature is, and how quickly it is reached, depends on the thermodynamic properties of the two bodies. The important properties are temperature, density, specific heat capacity, and thermal conductivity.
   BULLET::::- PP and PP copolymers
  
  BULLET::::- ABS and PMMA
   Metal fires represent a unique hazard because people are often not aware of the characteristics of these fires and are not properly prepared to fight them. Therefore, even a small metal fire can spread and become a larger fire in the surrounding ordinary combustible materials. Certain metals burn in contact with air or water (for example, sodium), which exacerbates this risk. Generally speaking, masses of combustible metals do not represent great fire risks because heat is conducted away from hot spots so efficiently that the heat of combustion cannot be maintained. In consequence, significant heat energy is required to ignite a contiguous mass of combustible metal. Generally, metal fires are a hazard when the metal is in the form of sawdust, machine shavings or other metal "fines", which combust more rapidly than larger blocks. Metal fires can be ignited by the same ignition sources that would start other common fires.
   Electrical firemaking involves the contact of an electrically heated object to tinder. A current is run through the object until it is red hot, like the burners on an electric stove, and it is brought into contact with the tinder, lighting it. For example, a foil-paper chewing gum wrapper will heat-up and ignite; or a flashlight battery coming into contact with a thin wire mesh (such as steel wool) may produce enough heat to ignite charcloth or other tinder. Larger batteries can generate sparks when its leads touch.
  
  Section::::See also.
  
  BULLET::::- Glossary of firelighting
  
  BULLET::::- Quest for Fire (film)
   The arc caused during the contact break (break arc) is similar to arc welding, as the break arc is typically more energetic and more destructive. The arc can cause material transfer between contacts. The arc may also be hot enough to evaporate metal from the contact surface.
  
  The high temperatures can also cause the contact metals to more rapidly oxidize and corrode.
   Some fire-starting systems use a ferrocerium rod and a hard scraper to create hot sparks by manually scratching the ferro rod with a knife or sharp object to ignite man-made or natural tinder. Fire starters based upon ferrocerium are popular with bushcraft hobbyists and survivalists. Similar sparking devices have a built-in striking blade which provides an easy method for sparking with one hand. Another common type has the ferrorod attached to a magnesium bar that can be scraped with a knife to make a powdered tinder that will burn for a few seconds.
  
  Section::::Methods.:Percussion.:Lighters.
   Section::::Smithing process.:Welding.
  
  Welding is the joining of the same or similar kind of metal.
  
  A modern blacksmith has a range of options and tools to accomplish this. The basic types of welding commonly employed in a modern workshop include traditional forge welding as well as modern methods, including oxyacetylene and arc welding.
  
  In forge welding, the pieces to join are heated to what is generally referred to as "welding heat". For mild steel most smiths judge this temperature by color: the metal glows an intense yellow or white. At this temperature the steel is near molten.
   BULLET::::- Beverage can stove
  
  BULLET::::- Billycan
  
  BULLET::::- Campfire
  
  BULLET::::- Cooking in tinfoil pockets
  
  BULLET::::- Cooking with green-sticks
  
  BULLET::::- Steaming food in appropriate green leaves
  
  BULLET::::- Using a metal grill
  
  BULLET::::- Using thin rocks as a skillet
  
  BULLET::::- Cook stove
  
  BULLET::::- Hobo stove
  
  BULLET::::- Portable stove
  
  BULLET::::- Rocket stove
  
  BULLET::::- Shichirin
   Extrusion process can be done with the material hot or cold, but most of the metals are heated before the process, if high surface finish and tight tolerances are required then the material is not heated.
   Section::::Operating and design principles.
  
  In normal use, electrical equipment often creates tiny electric arcs (internal sparks) in switches, motor brushes, connectors, and in other places. Compact electrical equipment generates heat as well, which under some circumstances can become an ignition source.
  