Everywhere else, the heat spreads very slowly. It is important that the shuttle tiles are made of such a material. When the space shuttle is returning to Earth through the Earth's atmosphere, the outside of the shuttle gets very hot. In order to keep the astronauts inside the shuttle from burning up, the shuttle must be covered in a material which does not allow heat to move through it very easily. The thermal current is directly proportional to the coefficient of thermal conductivity.
Different materials have different coefficients of thermal conductivity.
The shuttle tile is made of a material which is a silica, alumina fiber and borosilicate glass composite. The shuttle tile is a material which has a very low coefficient of thermal conductivity. When one spot of the tile is heated by the propane torch, the thermal current inside of the tile is therefore very low. The thermal current from the tile and through the air is actually higher. Since the thermal current is so low, only the portion of the tile very near where the tile was directly heated has been affected by the heat.