Ok so I just had a lasagna in the oven for 45 minutes, covered in foil. I pulled it out and the tin foil isn’t even warm. How?
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The aluminum has a high thermal conductivity. This means that it releases heat extremely well. So when it heats up it doesn’t hold onto it for long. Another cool fact!
If you heat copper and aluminum to the exact same temp, the aluminum would release it so much faster that it would cause worse burns. I found it cool since you pull it out of the oven and it isn’t hot.
Aluminum is a very good conductor of heat and anything that absorbes heat quickly will also shed that heat just as quickly. Add that the foil is very thin and it wont stay hot but for a minute or two.
Alum is 3rd behind silver and copper for heat dissipation and its relatively low cost is why it is used for heat sinks in electronics and computers
How overdone is that lasagne?
45 minutes in the oven doesn’t sound right, unless you had the oven turned low
It’s very low mass which means that it contains very little heat energy. Your hands just soak it up and only get a teeny tiny bit warmer. As others have pointed out it also conducts heat very well. Combined with the low mass and large surface area this means it will quickly cool down to room temperature.
There are actually 2 different reasons for this. Specific heat, and mass. Specific heat is how much heat a material can hold. A ceramic casserole dish can hold a lot of heat. If you grab it when its hot it has a huge reservoir of heat that will travel to your body (heat always travels towards the colder object). Aluminum has extremely low specific heat and it cannot hold much heat. It’s reservoir is small and when it travels to your hand it’s not enough heat to even register as being warm. Note: others have talked about conductivity. This is related, but slightly different. I actually just answered [a similar question](https://www.reddit.com/r/explainlikeimfive/comments/lx93lu/eli5_why_does_metal_feel_cold_or_wet/) in this sub about conductivity.
The other variable that effects the size of that reservoir is the total mass of the object. Aluminum foil is very thin and its total mass is very low. A low mass with a low specific heat means that very little heat will transfer from it to a colder object (i.e. your hand).
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