Odd fact that i have only just learned after being on this planet for nearly 70 years.
People often don't know whether to use tin foil with the shiny side up or down. The shiny side is only created by the rollers as it is fed through when it is being made. There is absolutely no difference how you use it, although I do think if you have the shiny side out it reflects the heat whereas if you have the shiny side down it absorbs the heat better I think, but experts say it doesn't matter which way you have it.
Another piece of useless information from yours truly