First of all lets clarify two basic facts: Aluminum foil always has two sides with different surface characteristics. One of the sides is shiny polished and the other is left matt (no post-treatment). read more
A piece of aluminium foil held in front of the grill may now be used to reflect the heat from the element on to your hand where the warming effect may be easily detected. I have tried this but have been unable to find any difference between the heat reflected by the dull and shiny sides. read more