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A Superheated DebateDate Added: Apr. 24, 2001
There's a common misconception that Urban Legends, by definition, are false. That has led many to argue this chain's place in the BreakTheChain.org hall of shame. I feel that the following is information, that anyone who uses a microwave oven to heat water should be made aware of. About five days ago my 26-year old son decided to have a cup of instant coffee. He took a cup of water and put it in the microwave to heat it up (something that he had done numerous times before). I am not sure how long he set the timer for but he told me he wanted to bring the water to a boil. When the timer shut the oven off, he removed the cup from the oven. As he looked into the cup he noted that the water was not boiling but instantly the water in the cup "blew up" into his face. The cup remained intact until he threw it out of his hand but all the water had flew out into his face due to the buildup of energy. His whole face is blistered and he has first and second degree burns to his face, which may leave scarring. He also may have lost partial sight in his left eye. While at the hospital, the doctor who was attending to him stated that this a common occurrence and water (alone) should never be heated in a microwave oven. If water is heated in this manner, something should be placed in the cup to diffuse the energy such as a wooden stir stick, tea bag, etc. It is however a much safer choice to boil the water in a teakettle. Later versions of this chain included various added "evidence" of the phenomenon: GENERAL Electric's RESPONSE: Thanks for contacting us, I will be happy to assist you. The e-mail that you received is correct. Microwave water and other liquids do not always bubble when they reach the boiling point. They can actually get superheated and not bubble at all. The superheated liquid will bubble up out of the cup when it is moved or when something like a spoon or tea bag is put into it. To prevent this from happening and causing injury, do not heat any liquid for more than two minutes per cup. After heating, let the cup stand in the microwave for thirty seconds before moving it or adding anything into it. --- Here is what our local science teacher had to say on the matter: "Thanks for the microwave warning. I have seen this happen before. It is caused by a phenomenon known as super heating. It can occur anytime water is heated and will particularly occur if the vessel that the water is heated in is new, or when heating a small amount of water (less than half a cup). What happens is that the water heats faster than the vapor bubbles can form. If the cup is very new then it is un! likely to have small surface scratches inside it that provide a place for the bubbles to form. As the bubbles cannot form and release some of the heat that has built up, the liquid does not boil, and the liquid continues to heat up well past its boiling point. What usually happens, when the liquid is bumped or jarred, just enough of a shock to caus the bubbles to rapidly form and expel the hot liquid. The rapid formation of bubbles is also seen when carbonated beverage spews when opened after having been shaken." If you pass this on ... you could very well save someone from a lot of pain and suffering. Basically, what is suggested here is accurate. In order to boil, water must have a "nucleation point" - simply heating it beyond the boiling point is not enough. Imperfections in the container or motion created during the heating process usually provides the nucleation required for boiling. Water could very well be superheated in a very clean cup with no imperfections in a smooth-running microwave oven. If disturbed in its superheated state (by inserting a spoon or adding instant coffee), the stored energy can be released at once. Only a small fraction of the water turns to steam, but may be enough to dispell a significant amount of water a substantial distance. I have received a lot of flack for including this chain on BreakTheChain.org. Many think that, since the warning is basically accurate, there is nothing wrong with forwarding it. But BreakTheChain.org looks beyond the simple truth or falsehood of a message to the appropriateness of e-mail for distributing the information. That is where this one fails. If this "true story" has made you nervous about heating water in the microwave, that's probably a good thing, but please don't take an ounce of truth to mean this message is unimpeachable. Many urban legends, especially those that warn of some everyday risk to your health, are based on things that are real. The legend lies not in the facts, but in how the story is told. The original chain letter above has several of the most common legend components:
Urban legend chains often take events that could happen and assert that they have happened through an emotion-provoking third person account. Why? Because most of us will ignore a warning unless we can visualize it. Yes, it is technically possible to be badly burned by superheated water, but it is equally likely that a gang member could Slash your ankles or a deranged sociopath could put used hypodermic needles on gas pump handles. Many people are burned badly each day by boiling water, heated in the microwave and on the stovetop. Accidental spills and steam burns account for many more water burns than superheating. E-mail chain letters are a terrible tool for spreading health warnings, and BreakTheChain.org strongly advises against relying upon them for any advice affecting your health. Already, we can see that this chain has morphed beyond its original. Recent versions further omit any verifiable information, such as the reference to 5 days ago and the relationship of the alleged victim to the author. For many, the microwave is still a thing of mystery. We heard the horror stories as children: "Don't stand too close, the radiation will make you sick," or "Stick aluminum foil in it and it will catch fire." Both are compelling and "possible" (though only under extremely rare circumstances), but imagine how much more convincing they'd be if given in the form of a story of a boy that got skin cancer by standing too close to a microwave, or a tale of the worker who burned down his office building by nuking a piece of leftover chicken wrapped in foil. Neither is true or likely, but both are "possible" and people are more likely to forward them than a scientific or technical explanation. Most microwave user's manuals recommend letting any food item stand for several minutes after heating before removing it from the oven, for safety's sake. But how many of us actually read the manual? Now, how many of us will read a chain letter marked "URGENT, MUST READ!!!"? Thought so. Break this Chain. |