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+--- Thread: When using aluminum foil, does the orientation of the shiny side vs. the dull side ma (/Thread-When-using-aluminum-foil-does-the-orientation-of-the-shiny-side-vs-the-dull-side-ma)
When using aluminum foil, does the orientation of the shiny side vs. the dull side ma - haomeialu - 12-18-2017
Like a lot of questions, the answer is “it depends”. Mattering depends on the observer. These guys Foil: Shiny side up or down? ran some tests and concluded that for several cooking processes that if there is a difference it is very small. How small a difference doesn’t matter? That is up to the observer to define.
Mechanistically, it shouldn’t matter for heat transfer by conduction. For heat transfer by convection, it probably makes a small difference. I would lean toward dull side facing the heat source based on turbulent boundary layer considerations. For heat transfer by radiation, dull side facing the heat source should reflect slightly less and heat slightly faster. If food is wrapped in foil, heat transfer from foil to food will likely be a mixture of conduction where food is in contact with foil, and radiation where it is not. I would not expect much contribution from natural convection. I would also expect that the effect of degree of crinkling of the foil in applying it to food would swamp the small differences between dull and shiny side out.
If you are making a hat from the foil, I would go with shiny side out.