Please explain some of the sounds that a kiln makes.

We can often tell when something is about to fail on a car by the sounds it makes. Sometimes kilns give warning sounds, too. Here are some of the sounds that a kiln makes:

1. The elements on some kilns hum when they turn on. This is because they vibrate in the brick grooves due to magnetism between the coils. This sound is normal.
2. The clicking noise of a manual fire kiln is also normal. It is the sound of an infinite control switch cycling on and off. Each time the switch turns on the power, the elements may also hum. When the clicking turns into a popping noise, the switch is probably about to fail. You should keep a spare one on hand.
3. Another source of clicking is from the relay, which is found on digital kilns and a few manual fire kilns. To turn on the elements, a digital controller sends 12 volts to the relay. The relay, in turn, sends full voltage to the elements. Every time the relay turns on, it clicks. (Note: mercury relays are silent.) If you hear a chattering noise, the relay is about to fail. Keep a spare one on hand.
4. A popping from inside the kiln may beware exploding due to moisture in the clay. During the initial heating stage, water expands. If the kiln heats slowly, the water evaporates harmlessly. If the kiln heats too fast, the water inside the clay blows up. Dry the greenware before firing, vent the kiln and fire slowly.
5. A loud POP from the kiln’s switch box usually means that a loose electrical connection has just failed. This is sometimes preceded by a crackling noise. If you hear crackling, which sounds like sparks, turn off the kiln.

The loose connection creates a tiny electrical arc, which overheats and fails. A rapid arcing causes the popping noise. Whenever you change elements or have the switch box open for any reason, check all the wire connections. Make sure they are tight. (The power must be disconnected, of course.) Tug on the wires. If a wire pulls out of a terminal, replace the terminal with a new one using a good crimping tool. Remove dust before closing the switch box. When you replace elements, make sure the connections are tight.