They are a much better heat conductor than an equivalent cross-section of solid copper.
Ceramic is a fairly poor heat conductor, so the material gets quite hot during operation.
Most bridges today are built with steel and concrete, both of which are good heat conductors.
Since scale is a poor heat conductor, inefficient fuel usage soon becomes apparent.
These tiles were such poor heat conductors that one could hold one while it was still red hot.
As opposed to air cooling, water is used as the heat conductor.
In the case of convection, we want to use a poor heat conductor with many dead air spaces within it.
Solid rock was a better heat conductor than sand.
Calm and undisturbed water is a relatively bad heat conductor comparable with glass, bricks, soil.
Even though the cast iron itself is a poor heat conductor, the oil makes the pan effective when it is at a high temperature.