Insulation MaterialThere are two types of insulation used in portable propane campfires: High temperature ceramic fiber, and loose granular vermiculite. High temperature ceramic fiber was originally designed for the space shuttle. It is lightweight, lasts indefinitely, reflects high heat, and cools down quickly. It is expensive but is the perfect insulator for a portable propane campfire.
Loose granular vermiculite is a low cost naturally occurring substance. Mined at the same place that asbestos is mined, vermiculite can contain asbestos fiber and asbestos dust. If piled deep enough, it is a good insulator. It should be kept out of the wind as it will blow around.