You can purchase a toaster at any discount store for less than $20 (U.S.). The particular model shown on the right allows you to set the darkness of the toast it produces and also has a defrost mode.
The basic idea behind any toaster is simple. A toaster uses infrared radiation to heat a piece of bread (see How Thermoses Work for information on infrared radiation). When you put your bread in and see the coils glow red, the coils are producing infrared radiation. The radiation gently dries and chars the surface of the bread.
The most common way for a toaster to create the infrared radiation is to use nichrome wire wrapped back and forth across a mica sheet, like this:
Nichrome wire is an alloy of nickel and chromium. It has two features that make it a good producer of heat:
- Nichrome wire has a fairly high electrical resistance compared to something like copper wire, so even a short length of it has enough resistance to get quite hot.
- The nichrome alloy does not oxidize when heated. Iron wire would rust very quickly at the temperatures seen in a toaster.
The very simplest toaster would have two mica sheets wrapped in nichrome wire, and they would be spaced to form a slot about an inch (2.5 cm) wide. The nichrome wires would connect directly to a plug. To make toast:
- You would drop a piece of bread into the slot.
- You would then plug in the toaster and watch the bread.
- When the bread became dark enough, you would unplug the toaster.
- Then you would tip the toaster upside down to get the toast out!
Most people don't have this sort of patience, nor do they like crumbs all over the counter. So a toaster normally has two other features:
- A spring-loaded tray pops the toast out. This keeps you from having to turn the toaster upside down.
- A timer turns the toaster off automatically and at the same time releases the tray so the toast pops up.