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LGBurns
03-28-2001, 05:24 PM
Okay, I received the following as an e-mail (danger, Will Robinson, danger!) and I swore I would never post another e-mail health warning again after my last ovarian cancer fiasco on the Healthy Living board but I checked this out and it really is copied directly from the ABC.com website. Thought it might be useful info for you all.

Explosive Microwave Danger
'Superheating' Can Cause Violent Bubbling


March 15 — Patty Long put water in the microwave and waited three minutes for it to boil, but something seemed wrong: no bubbles.

So she heated the water a little longer. When she took it out, Long recalls, the water "exploded like a bullet up into my face. It hit the ceiling too."
Long was rushed to the emergency room, where she was treated with first- and second-degree burns all over her face. Even worse, the corneas of her eyes had been scalded.
"I was afraid I would never see my kids again," says Long, who lives in Naperville, Ill. It took six months of treatment for Patty to fully recover her sight.
Boiling Without Bubbles
Experts say that what caused Long's injury is known as "superheating," which is one of the most potentially hazardous problems that can occur when heating water or other liquids in a microwave oven.
The scientific definition of superheating is that water can go above boiling temperature without any bubbles forming. "It's hotter than it should be for normal boiling to occur, and yet it doesn't boil," say Louis Bloomfield, physics professor at the University of Virginia. In a process called nucleation, the energy that's already in the water, however, can be triggered by a granule — such as a tea bag, instant coffee or a utensil — which can then cause the water to erupt.
"Anything that triggers the boiling once you've reached that temperature will cause catastrophic, very sudden flash boiling," explains Bloomfield. "And it can spray the water … all over the room, the microwave or you."


Preventing Microwave Hazards

Despite this danger, Bloomfield says a microwave is "actually one of the safest devices in your kitchen when used correctly." Here are some tips to prevent superheating and other microwave problems:

Put your teabag or instant coffee in the water prior to heating the water in the microwave.

Always stir liquids before heating, suggests CiCi Williamson, food safety specialist at the USDA.

Don't put twist ties in the microwave. "It's like a wire with too much electricity running in it," says Bloomfield. "The charges pile up at the ends of that twist tie and can potentially make sparks."

Don't cook things too long. Sounds simple, right? But many people don't pay attention to how long they heat something for in the microwave. According to the Association of Home Appliance Manufacturers, you should not heat liquid for more than two minutes.

Stir food midway through cooking to distribute heat and homogenize the temperature. Unlike a conventional oven, a microwave heats food from the inside out, rather than from the outside in. So the container may be cool but the contents beyond boiling temperature.

Allow standing time before touching. "A decent rule of thumb is to wait maybe a minute or two for every cup of water you've got," says Bloomfield, "to give it time for the evaporative process to cool down the liquid and bring it back toward the boiling temperature from above."

Sample food before giving it to a child or test the temperature and several places. "Until you stir it and then feel it carefully," says Bloomfield, "you don't know what the temperature of that next spoonful is."

Do not let plastic wrap touch foods during microwaving and be sure to use a brand of plastic wrap that is microwave-safe.

Loosen the plastic wrap on one corner. "Turning a corner gives the steam a vent to escape, while keeping most of it in," says Williamson.

Lift a lid or plastic wrap away from your face. "Don't look at it while your lifting it," advises Williamson. "And start from the back of the dish."

Keep children away from microwaves when removing hot liquid or food.

Use a baby bottle warmer instead of heating a bottle in the microwave, as some formula and botles have disposable plastic liners may be problematic.

Don't microwave in Styrofoam.

Do not dry herbs in the microwave, as they can ignite.

Use a turntable inside the microwave to keep the liquid moving and to promote more even heating, says Terry Dunn, General Electric's general manager of global communications.

— ABCNEWS.com's Rebecca Raphael contributed to this story.


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Zinnia
03-29-2001, 03:47 AM
I saw the story about microwave dangers last week on Primetime (the one w/ Diane Sawyer &
Charlie Gibson). I was amazed at the stories of the two women who were hurt heating water in their microwave! And it was scary to think of how many times I've done it-I don't "see" the water boiling in the cup, so I add another minute or so.. I will NEVER do that again! TY LGBurns for posting this, it's so important for people to know.. http://www.cookinglight.com/bbs/smile.gif Zinnia

Julie O
03-29-2001, 05:23 AM
This phenomenon is VERY rare, but it really can happen. It's caused by heating water in a container that has too smooth of a surface. Water needs nucleation sites for boiling to begin. A nucleation site can be as simple as a scratch on a container from where a spoon touched it. Without the nucleation site, the water will get hot enough to boil, but it won't actually boil. Then, when the container is disturbed, such as by movement, the boiling begins, but VERY rapidly. So rapidly that the water can actually come out of the container within seconds.

Just be careful when you have new containers. If you have an old, grungy coffee cup, you should be fine.

makedah
03-29-2001, 06:58 AM
I've actually experienced this, with all the cupa soups I make. Pour a few granules of that in there and LOOK out! Also, I've heard the water 'explode' in the microwave after being in there too long. I know now that it takes my mug of water 3-3.5 min in the microwave to get hot enough (now I know why I don't always see bubbles, thanks!) and why it froths up when I add my tea bag.

About tea bags... I'm surprised they didn't warn you about adding them before you nuke the water because of that little (metal) staple in them.

Vanessa
03-29-2001, 09:27 AM
Hi. I saw that program too. Actually I got worried enough that I started heating soup the old fashion way (stove) http://www.cookinglight.com/bbs/smile.gif

schuh
03-29-2001, 10:21 AM
I'm just wondering -- has anyone had a similar experience with the really smooth, straight-sided All-Clad saucepans on the stove?

I've noticed that when I'm cooking liquids/sauces, they will seem like they aren't doing anything. Then, when I put a spoon in to stir, the liquid bubbles up like crazy. It has made me nervous -- I make sure I stir frequently in them -- but I wonder if super-smooth pans can have the same effect.