Fire-walking

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Fire-walking is the act of walking barefoot over a bed of hot coals. When done properly, it does not pose any serious risk of burning one's feet; it does not require any extraordinary mental state, but can be dangerous if done without sufficient understanding and care.

[edit] Application

Fire-walking is practiced

by fakirs and similar persons,
in management seminars and motivational seminars, such as those conducted by Anthony Robbins, Alan Lowis, Peggy Dylan, Tolly Burkan, Tomorrow's Youth etc., Empower U
by Eastern Orthodox Christians in parts of Greece and Bulgaria during some popular religious feasts (see nestinarstvo).
the African-born Hindus walk on fire regularly as part of important religious festivals
!Kung Bushmen of the African Kalahari desert have firewalked since their tribal beginnings. The !Kung use fire in their healing ceremonies.
by Japanese Taoists and Buddhists
as a rite of purification, healing, initiation and transcendence.

Organizers of firewalking ceremonies sometimes claim that in order to prevent one's feet from burning, meditation, calling on spirits or gods or other supernatural intervention is necessary.

The oldest recorded firewalk occurred over 4,000 years ago in India. Two Brahmin priests were competing to see who could walk farther over hot coals. The victor's triumph was recorded in writing surviving to this day.^{[citation needed]} In a 17th century letter, Father Le Jeune, a Jesuit priest, wrote to his superior, telling of a healing firewalk he witnessed among the North American Indians. He reports of a sick woman walking through two or three hundred fires with bare legs and feet, not only without burning, but all the while commenting on that she could feel no uncomfortable heat. Some 30 years later, Father Marquette reported similar firewalks among the Ottawa Indians and Jonathan Carver writes in his 1802 book, Travels in North America that one of the most astounding sights he saw was the parade of warriors who would "walk naked through a fire...with apparent immunity."

[edit] Physical 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, mass, specific heat capacity, and thermal conductivity.

The product of mass and specific heat capacity is called heat capacity and tells us how much heat energy the body needs to heat it up by one degree. Since the heat taken in by the cooler body must be the same as the heat given by the hotter one, the end temperature will lie closer to the temperature of the body with the greater heat capacity.

The bodies in question here are human feet, which mainly consist of water, and burning coals.

Several factors act together to prevent the foot from burning:

Water has a very high heat specific capacity (4.18 kJ/K kg), whereas coals have a very low one. Therefore the foot's temperature will change considerably less than the coal's.
Water also has a high thermal conductivity, and on top of that, the blood in the foot will carry away the heat and spread it. So effectively the mass of the cooler body is increased. On the other hand, coal has a poor thermal conductivity, so the hotter body consists only of the parts of the coal which is close to the foot.
When the coal cools down, its temperature sinks below the flash point, so it stops burning, and no new heat is generated.
The coals are often covered with ash, which is a poor heat conductor.
The coals are a very uneven surface, and the actual surface area of foot touching the coals is very small.
Firewalkers do not spend very much time on the coals, and they keep moving.

There are risks when doing fire-walking improperly:

People have burned their feet when they remained in the fire for too long, enabling the thermal conductivity of the coals to catch up.
Foreign objects in the coals may result in burns. Metal is especially dangerous since it has a high thermal conductivity.
Coals which have not burned long enough can burn feet more quickly. Coals contain water, which increases their heat capacity as well as their thermal conductivity. The water must be evaporated already when the firewalk starts.
Wet feet can cause coals to cling to them, increasing the exposure time.

It has been claimed that the Leidenfrost effect, which is based on a layer of water vapor between the hot and cold body, is involved in firewalking.^{[citation needed]} This claim remains controversial. Some detractors state that if the Leidenfrost effect was operating the effect would create greatly reduced friction, making the coals slippery to the feel, which has not been observed.