Need boiling water for a recipe or drink, but don't want to go to the trouble of using the stove? Luckily, a small amount of water can reach the microwave boiling point in a matter of minutes, but not without its downside: without proper procedure, there is a small (but real) risk of overheating - a phenomenon in which too much steam is released quickly and causes water to overflow upwards, which can cause burns. As unlikely as this occurrence is, just take some precautions to safely boil water in the microwave!
Choosing a microwave safe container
Choosing a container is the first step in safe microwave use. Read the table below to find out if your vessel material is suitable.
|Material||Safe for the microwave?||Observation|
|Most metals (including aluminum foil and silverware)||Not||Metals can cause sparks that may damage the microwave or cause a fire.|
|bread paper bags||Not||In addition to the risk of fire, this material can release toxic gases.|
|Vacuum-capped or closed containers||Not||Probability of explosion due to accumulation of vapors inside.|
|Disposable containers (yoghurt cups, margarine jars, etc.)||Not||They can melt, catch fire or emit toxic gases.|
|Plastic (Tupperware and related products, plastic film etc.)||Not recommended||There is evidence (though not definitive) that when used in the microwave, the plastic these containers are made of release toxins that contaminate the food. Some of these products, however, are manufactured to parameters that make them microwave safe.|
|Polystyrene||Not recommended||As in the item above, only some types of Styrofoam do not pose a risk when used in the microwave.|
Part 1 of 2: Safely Boiling Water
Step 1. Pour the water into a microwave-safe cup or bowl
Boiling water in the microwave is absurdly easy (even when all safety measures are taken). First, make sure the container is made from one of the safe materials listed above.
Do not use anything that is closed or capped. Accumulation of vapors could cause a dangerous explosion
Step 2. Place a microwave safe object (something non-metallic such as a wooden spoon, chopstick, or an ice cream stick) in the water
This encourages the water to bubble and prevents it from overheating.
- Overheating occurs when water passes the boiling point but cannot bubble due to the lack of "nucleation" points (irregularities to which steam can adhere and form bubbles). As soon as the water is disturbed or a nucleation point forms, the vapor suddenly appears and causes a small explosion of boiling water.
- If you don't have anything non-metallic that you can put in the water, use a container whose insides are scratched or peeled. These parts serve as nucleation points.
Step 3. Place the water in the microwave
Heat the water in "steps" (never longer than a minute and a half), always stirring the liquid between them, until the boil starts. Even following these instructions, the boiling water may not be as noticeable compared to when it is heated on the stove. The best way to make sure your water is boiling is to use a thermometer. At sea level, the boiling point is at 100 °C and decreases the higher the altitude.
If the container material easily retains heat (such as glass and ceramic), be careful when removing it from the microwave for stirring. Protect your hands with a dish towel or oven mitts
Step 4. If the goal is to sterilize the water, keep it boiling longer
Sterilization is the name given to the process of boiling water long enough to eliminate any micro-organisms. For this purpose, it is recommended to boil the water continuously for at least 1 minute (or 3 minutes at altitudes greater than 2000 m).
Part 2 of 2: Avoiding the Dangers of Overheating (more tips)
Step 1. Do not heat the water for excessively long periods
If, after following what is recommended in the above section, the possibility of overheating still worries you, just take a few more steps to increase your safety. Perhaps the biggest one is never uninterruptedly heating the water for long. Not interrupting the process to stir the water decreases the chances that it will boil, which in turn increases the chances of overheating.
The time-out for each "step" of water heating can vary depending on the microwave oven power. To maximize safety, start by heating the water for a minute or less. Depending on how hot it gets, adjust the timeout to more or less
Step 2. Avoid extremely smooth and even surface containers
The same reason why placing a non-metallic object in water or using scratched containers is recommended makes very smooth containers a bad idea. The biggest examples of what not to use are new, highly polished glass or ceramic bowls, although other materials can also cause problems.
Instead of a new bowl, use an older, worn one with visible scratches on the bottom that serve as nucleation points for the steam
Step 3. Gently drum the container at the end of heating
As soon as you think the water is hot enough, tap the pan wall firmly before removing it from the microwave oven - to protect your hands, use a long instrument to perform this step.
If the water is overheated, the impact on the edge of the container will cause the surface of the water to "explode". This can get the inside of the microwave wet, but it will keep you from getting burnt
Step 4. Stir the water with a long object while it is still in the microwave
Still not sure the water isn't overheated? Use something long (a stick or a large skewer) to stir the water. This movement creates spaces where steam can collect and form bubbles - and if the water is really overheated, it will either explode or start boiling sharply. If not, congratulations! It is safe to approach water.
Step 5. Turn your face away from the container until you are sure it is secure
This tip seems obvious, but it can't be stressed enough: don't point your face in the direction of the water while there is minimal risk of it being overheated. Most injuries from overheating happen when people take water from the microwave and look directly at it. At that distance, a sudden explosion can cause severe burns and, in the most severe cases, permanent loss of vision.
- A mug of water without something in it, such as chopsticks, poses a great risk of overheating because there are no holes where bubbles can form. Putting a toothpick in water, for example, requires almost no time and effort, but it can save you a lot of trouble.
- Never place a closed container of water in the microwave - it will explode due to the accumulation of vapors, causing a nice mess!