Neither paper nor plastic are good conductors of heat. In fact, they are both insulators. This means they resist the flow of heat.

Here's why:

* Paper: Made from plant fibers, paper is porous and contains air pockets. Air is a good insulator, so paper helps to slow down the transfer of heat.

* Plastic: Many types of plastic are designed to be insulators. They have a structure that traps air, making them effective at preventing heat transfer.

Good conductors for keeping things cold are materials that readily transfer heat. Examples include:

* Metals: Aluminum, copper, and stainless steel are excellent conductors. That's why metal containers are often used to store cold items.

* Water: Water is a relatively good conductor, though not as good as metals.

To keep things cold, you want to use an insulator, like paper or plastic, to prevent heat from getting in.