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Foil on bottom of oven

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I have a foil sheet on my lower oven rack to protect against spills onto the heating element. Lately, I've been thinking that this is affecting my baking. Is this a possiblity or likely just in my head?

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  1. Good question. I can testify that dirty dark pans cook much better than bright shiny new ones. The inside of ovens are usually black (can't remember seeing stainless steel) so maybe there's a good reason it's so dark in there.

    1. I had a foil sheet in the bottom of my oven. I had a repairman over because my oven temp wasn't working well. He did his tests and they came back normal. He told me to take the foil out as it affects the temperature. I did and I had not problems after that.

      1. You can buy a silpat oven liner that won't affect the temperature.

        http://www.williams-sonoma.com/produc...

        1. bmorecupcake, I've had the bottom wire shelf covered in aluminum foil for ages, and have never had a problem with cooking or baking.

          2 Replies
          1. re: dolores

            I'd think it would make a big difference depending on having electric stoves or gas. The thermostat location is one factor, as would be the "over temperature switch" that protects electric elements from burning out. Because gas stoves have to vent the combustion gases the oven chamber is not really sealed -- thus the foil ought not block that venting.

            1. re: dolores

              You're lucky. Thermal convection is directly affected by cavity depth. Covering those wire racks limits the scale of the oven cavity. If you have convection, this is a much more serious problem.

            2. I made Lindsey Shere's almond tart out of "Alice Waters and Chez Panisse" last weekend, and one of the instructions is to place the foil for catching drips with the shiny side down because she says the reflection on the shiny side can affect your oven's thermostat. Amazing. Who knew? (Lindsey Shere and Three-of-us's repairman, apparently!)

              1. Never put foil in the bottom of your oven. It does reflect heat and affect your baking. Ya just have to clean it up!

                1. I keep a baking stone on the bottom rack of my oven. More to help regulate the temperature, for when I open the oven but it helps with spills, too (and gives me a place to keep it).

                  1. I've seen reports - In different context - that the difference in reflected heat is actually quite small when actually measured so I'm not sure how much reflection is the issue. On the other hand, it would certainly affect air circulation if it's covering the whole rack from side to side, front to back - I think if you leave an inch or 2 around the edges, it might be less of a problem. I don't these days, but I also kept a baking stone on the lower rack for a few years and it was never a problem, but it only covers about 3/4 of the rack.

                    Putting foil on the bottom of the oven itself is a different story and everything I've ever heard or read claims it can actually damage the oven though I don't remember why. I think it can do a couple of things including damaging the thermostat if that's on the oven floor (as it is in many electric/top broiler ovens) and I think it can also prematurely age/damage the burner unit in bottom-broiler (gas mostly) ovens if you block the sides and circulation holes - generating too much heat in the broiler area to maintain temps in the oven..

                    I sometimes stick a loose sheet of foil on the bottom, temporarily, if I'm cooking something very messy and need both racks. That's never been a problem, but I don't leave it there all the time, don't form fit it to the whole bottom and definitely don't block the holes on the bottom of my bottom-broiler oven.