When toasting a single piece of bread, why does it matter which slot you put it in?

Dear Matthew Alice:

I've recently purchased a lovely new toaster from my neighborhood Target. My toaster has two-slice capability, but I noticed there is a designated slot for the toasting of only one slice, and it is marked as such. What difference does it make which side I put the single slice of bread in, considering that both slots of the toaster glow hot no matter what?

-- Carl, the Net

Nothing like a new appliance to send the family into a frenzy of bewilderment. Assuming, of course, you did what we all do and pitch the box and instructions without reading them, then plug it in and wonder why it's suddenly burst into flames. Well, perhaps your toaster didn't have the explanatory note that some carry about the "one slice" slot. Though it does occur to me that you might have paid off the insurance policy, sent the kids to Grandma's, thrown caution to the winds, and tried toasting half a bagel on the wrong side to see what happens. Oh, well, easier to write to Matthew Alice, I guess.

If your toaster is the kind that lowers the bread automatically, saving you the hassle and exertion of pushing down a lever, then the bread-lowering mechanism is linked only to the toast hole marked "one slice." You could cram a loaf into the other and it wouldn't work.

If you have the push-it-down-yourself type, then the "one slice" sign marks the location of the thermostat. Bread toasts when the glowing elements heat the bread surface to about 300 degrees. At that temperature, the sugars and starches caramelize, and it's toast. Your model probably has a mechanical heat sensor only on the "one-slice" side, under the little bread elevator. If you sling one slice into the other side, the thermostat, uninsulated by bread, reaches its top temp too soon, shuts off the machine, and presents you with a piece of floppy, tepid un-toast. If you'd dug deeper into your wallet and bought a top-of-the-line model, it would have an electronic temperature sensor that would do everything but put on the butter and jam and cut off the crusts.