PROF'S POSER - Heat and rust

Ok, best I could do.

And wrong from the off, as aluminium doesn't rust.

However it does frame this Prof's Poser, which is essentially an enviROI-based one pondering energy consumption.

Over the weekend I was making an oven-heated meal. And it dawned on me that I was popping a sheet of foil in the glass dish.

Now the picture shows it all becomes moot pretty quickly anyway as the foil ripped, but I was wondering which was more energy efficient, and hence 'better': cook in foil and incur the costs of that resource being used and disposed of (there's a limit to how food caked it can be to [put out to] recycle), OR just use the glass and end up with a few pints of boiling water being required.