It contains minerals such as pyroxene, amphibole, feldspar and 63-68 percent silica. The eruption temperature for dacitic lava is 1,500 to 1,800 degrees Fahrenheit. Dacitic to rhyolitic lava is so dangerous because it contains a high amount of crystals.Mt. Vesuvius erupts according to the Plinian model of eruption.
Foil has low emissivity, so will greatly reduce radiative heat transfer (act like insulation). It should face the side that is supposed to be cooler. But foil will not reduce conductive heat transfer, so it must be used judiciously with something that reduces conduction.
Sometimes a thermally reflective surface called a radiant barrier is added to a material to reduce the transfer of heat through radiation as well as conduction. The choice of which material or combination of materials is used depends on a wide variety of factors. Some insulation materials have health risks, some so significant the materials are no longer allowed to be used but remain in use in some older buildings such as asbestos fibers and urea.