Metal is a good conductor – paper over metal gets burned slower

he paper over metal or over plastic/wood will get burned faster?

Everyone knows that metal is a good conductor of thermal energy. But for experiments like this, many would have guessed it wrongly.

A paper is wrapped over metal and insulator (plastic, wood etc) and is exposed to the flame, the paper over the insulator becomes charred faster and burned faster.

The paper over the metal takes a longer time to be charred and burned. This is because metal is a good conductor of thermal energy. When the spot (paper over metal) is exposed to the flame, the metal conducts the thermal energy away from that spot to other parts of the metal. So the temperature increase at that spot is slower, hence the ignition temperature of the paper (approx. 230oC) will be reached much slower, compared to the spot where the paper is over an insulator.