Water heated in a microwave can remain still above its boiling point if it has no rough spot where bubbles can form; this is called superheating. When a spoon is dipped into the water or the container is disturbed, the stored heat can turn to steam all at once, making the water erupt and spill out. To reduce the risk, place one wooden spoon in the container, keep the heating time short, and let the container stand.
Bubbles need a starting point when water boils; scratches or rough spots on the container, or tiny particles suspended in the water, usually provide one. In water heated on a stove, the bottom of the pot provides that rough surface and bubbles form steadily. In a microwave, the water heats from within and throughout the container; if the container is new and smooth and the water is clear, there may be no place for bubbles to start, so the temperature can rise above the boiling point. Still water inside the container increases this risk.
This is dangerous because the heat in the water is waiting to be released. When the container is shaken as it is removed from the microwave, a spoon is dipped into it, or something such as granulated sugar, coffee, or a tea bag is added, bubbles form suddenly and all at once; the water erupts out of the container. The splash can cause serious burns to the hand, arm, and face. Because the water looks still, a person may not notice the danger, which increases the risk. The highest-risk moment is near the end of the heating cycle, when the microwave door is opened.
The precautions are simple. Leave a microwave-safe wooden stick or spoon in the container while heating; its rough surface gives bubbles a place to start. New, unscratched glass and porcelain containers increase the risk, so lightly used containers may be preferable. Keep the heating time short and, if needed, divide it in half; if you do not know how long it takes to boil the water, heat it in 30–60-second intervals. Do not fill the container to the brim. If the same water were heated on a stove, the boiling would be visible and provide a warning.
Do not remove the container as soon as the microwave stops. Open the door and wait 30 seconds to let some of the superheated water bubble calmly. Hold the container by its rim, not over the top, and keep your face away from above it. If adding a spoon or tea bag to the water, first set the container on the counter, then add it slowly from the side. Do not pour fine particles such as sugar or instant coffee directly into the center of the container. This habit becomes routine quickly in a kitchen where water is heated for tea and coffee.
The same risk applies to liquids other than water. Oil, milk, and sugary liquids can also heat unevenly and boil over in a microwave; milk can form a skin on its surface, allowing pressure to build underneath. Heat these liquids at a low power setting, in short intervals, stirring in between. Never put a sealed jar, a tightly capped baby bottle, or an egg in its shell in a microwave; pressure builds inside them and the container can burst. Always leave a gap in the lid of a covered container.
Comments (2)
Aşırı ısınma diye bir şey olduğunu bilmiyordum. Suyu ısıtıp kaşık soktuğumda fokurdayarak taşmıştı, kazayı o zaman anlamamıştım. Neyse ki elim kabın uzağındaydı. O günden beri suyu mikrodalgada ısıtırken kabın içine bir çay kaşığı bırakıyorum.
Kaba tahta kaşık koymak gerçekten çözüyor mu, yoksa bu da anlatılan hurafelerden biri mi?
Çözüyor, çünkü kaşığın pürüzlü yüzeyi kabarcığın başlayacağı noktayı sağlıyor. Aynı işi kabın içine konan temiz bir çay kaşığı da görüyor. Asıl kural fırın durunca kabı bir dakika içeride bekletmek.