Got a stove with missing or broken dials? Until you replace them, you can still use the stove’s burners if you must (use pliers to turn the temperature knob shaft). But how do you know if you’re setting the temperature at high heat, low heat, or medium heat? What about medium-high or low-medium?
Put a pot of water on the burner. (Choose a sturdy saucepan with a heavy bottom; it will distribute heat evenly.) Small bubbles at the edges of the pot indicate low heat. Large, lazy bubbles across the surface of the water equate to medium heat. And once you see vigorous bubbles that don’t disappear even if you stir the water (a “rolling boil”), you’ve got high heat. You can adjust the temperature up or down by watching the bubbles increase or decrease.