[jws]

Plain old mechanical toaster trivia: The thermostatic element is placed in such a way that it is receiving reflected energy from the toast. As the bread dries and the Maillard reaction browns the toast it reflects more energy from the elements to the thermostat.

Viola! Toast browning detection in one bent piece of metal!

[cturner]

Darker things absorbed heat, rather than reflecting it - ? But then raw black bread will behave differently to raw white. Sounds interesting but I'm unconvinced.