So, to change the mood to something less serious: I toasted some raisin bread and forgot to reduce the heat setting on my toaster. It came out almost burnt. Far darker than the normal whole wheat toast I make. At the same setting the WW is lightly toasted.
Although my example is raisin bread, I’ve noticed that other breads like Italian-style also toast faster.
It got me to wondering:
*What is about certain bread types that cause them to toast so variably at the same heat settings? *
The raisin slice did not seem to be any less thick or weigh much less than my regular whole wheat, but TBH, I didn’t measure or weigh so it could be that.
Alternatively, I’m wondering if it’s some component of the flour or some other ingredient like added sugar?
The original darkness of the toast. White takes longer than brown, etc. Raisin bread is generally a bit darker, at least.
If you ever watch the color change while toasting you’ll note there’s no color change for quite a while and then whoop, it starts darkening quickly.
The combination of the heat maxing out, the toast starting to darken, etc. makes toaster design a lot harder than it looks. At one point the toast is lightly brown and a few seconds later it’s on the verge of burning.
Light-colored bread toasts slower than darker bread. Most of the energy in a toaster is optical - IR from the heating elements. A darker surface absorbs this much better than a lighter one, so a pumpernickel bread will that much faster than white bread.
I wasn’t thinking of color at all myself, and believe you are right that dark toasts faster, but I still think moisture is to blame for the sudden shift from “why isn’t it toasted” to “how did it suddenly burn?”