Saturday, 30 October 2010
01:03:03 PM (GMT)
Walking on fire has existed for several thousand years, with records dating back to
1200 B.C. Cultures across the globe, from Greece to China, used firewalking for rites
of healing, initiation, and faith.
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.
Factors that prevent burning
* Water has a very high specific heat capacity (4.184 kJ/K kg), whereas coals
have a very low one. Therefore the foot's temperature tends to change less than the
* 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, 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.
* Firewalkers do not spend very much time on the coals, and they keep moving.
* Calluses on the feet may offer an additional level of protection, even if only
from pain; however, most people do not have calluses that would make any significant
Risks when doing firewalking 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.
* One is more likely to be burned when running through the coals since running
pushes one's feet deeper into the embers, resulting in the top of the feet being
* 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.