Well that depends on who you speak to-According to a well known manufacturer of tin foil, there’s no difference between the dull side and the shiny side. The difference is caused in the final stage of making the foil, when two layers go through the rollers. The side that comes in contact with the roller comes out shiny and the side to the inside stays matte. But it doesn’t make any difference in how the foil is used.Then there is the general consensus that you need to direct the shiny side to where you want the heat to reflect to the most.
Our advice to anybody mulling over this dilemma is, do what works for you.