Overview
- Superheating allows water to exceed its boiling point without visible bubbles, creating a risk of sudden, violent boilovers that can cause serious burns.
- Simple disturbances can trigger the eruption, including moving the cup, inserting a spoon, adding sugar or coffee, or opening the microwave door.
- Risk increases with very smooth or thin-walled containers, small or narrow mugs, overheating for too long, and failing to pause and stir.
- The FDA and safety experts advise using microwave‑safe containers with some texture, heating in 30–60 second intervals with stirring, placing a wooden stick or spoon as a nucleation site, waiting 20–30 seconds before handling, and keeping your face away when opening.
- Boiling water in a microwave does not change its chemistry or make it less healthy, but a kettle or stovetop is recommended as a safer alternative when available.