(Dim)something strange is going on.

December 11, 2009 6:13 PM

This is a should I eat it?* question of sorts. Exactly how is my Chinese take-out place attempting to kill me?

Every time I order dumplings from the Chinese place up the street, I like to warm up the little plastic cup of sauce that comes with the order. I take the lid off, and stick the cup in the microwave for about 20 seconds.

Invariably, about 10 seconds into it, there's a zzzzzzzzap noise and occasionally a flash. I usually (stupidly?) let the microwave keep cooking until I hear a second zap, and then I take out the warmed sauce.

I know there's nothing metallic in the cup—no metal rim, for example. So what's in the sauce that could be causing the arcing? No other food does this in my microwave.

*I'm eating it.

posted by emelenjr to food & drink (14 answers total)

Wait, you put plastic in the microwave?
posted by roomthreeseventeen at 6:16 PM on December 11, 2009 [2 favorites]

Yeah, take it out of the container and put it in a cup. See what happens.
posted by bonobothegreat at 6:31 PM on December 11, 2009

roomthreeseventeen is right, unless it's marked, the plastic is not microwave safe, the sound you are hearing is the plastic melting. If you intend to heat the sauce, pour it into a microwave safe bowl.
posted by thebestsophist at 6:31 PM on December 11, 2009

Does the cup look melted or shrunk? Does the sauce explode? Fat will sometimes pop in nukers, too, but not usually in that short a time.
posted by Gilbert at 6:34 PM on December 11, 2009

Do you know what is in the sauce/what kind of sauce it is? Maybe someone with a chemistry/sciencey background can chime in if that is known. have you tried putting the sauce in a different container...not plastic. Maybe there is some weird reaction between the plastic and the sauce? Even if this is not the cause, which i doubt it is, it will keep you from heating the sauce in the plastic cup. Microwaving food in plastic is possibly not a good idea, health wise.
posted by Epsilon-minus semi moron at 6:36 PM on December 11, 2009

Wow, has it really taken me this long to discover non-microwave-safe plastic? The cup definitely doesn't look melted or shrunk. For reference, it's a typical translucent plastic cup that you might squirt some ketchup into.

I'll have to test the separate cup/bowl theory next time. I was convinced the dumpling sauce had something in it that was causing what sounds/looks like arcing. I'm not too sure of all the ingredients, but I'm guessing some soy sauce, something for a hint of sweetness, and what I believe were a few diced shallots. Your local Chinese takeout place of choice probably has the same sauce for its dumplings… it's pretty standard fare.
posted by emelenjr at 6:49 PM on December 11, 2009

I've seen weird stuff happen in my microwave with certain foods. Here's a page that talks about what grapes can do...so maybe there's a similar interaction with ingredients in your sauce.
posted by JibberJabber at 7:00 PM on December 11, 2009

Plastic can't be responsible for arcing in the micowave oven, because it can't directly absorb, reflect or focus energy from the microwaves, which are a form of radio and therefore a form of electromagnetic wave.Microwaves can only heat up metals or stuff made up of polar molecules, which plastics do not have. It needs to be something that can carry a current. Everyone knows that metals are great conductors - they absorb microwaves very easily, and so get very hot and are prone to arcing in microwave ovens. However, other conductors like sugary sauces (and molten glass!) also absorb the energy and can lead to arcing. As well as being really cool, that molten glass link actually has a nice explanation of what's going on and how microwaves will affect different substances.

Grapes and pickled onions can be made to arc in the microwave, at some risk of damaging your microwave: there's a nice explanation here. As I understand it, the small, round juicy conductors basically act similarly to lenses to focus the electric field, until a point is reached where the field strength in a certain area is strong enough to break down air into plasma, allowing electricity to flow. This means that the (positively charged) atomic nuclei are separated from their attendant (negatively charged) electrons, and these flow along the lines of charge. It involves a huge amount of energy and emits a lot of light and heat. That glowing arc of plasma is the spark that you see, and is exactly the same as a lightning bolt, albeit smaller.

While I can't find a decent write-up to link for you (or to refresh my memory), I have read previously that bits of food needn't be round, or even distinct objects. From memory, I think the idea was that a smallish patch of conductive material can quickly accumulate a huge amount of energy and charge, enough to briefly form a plasma with a pop and a visible flash. If there's nothing solid in your sauce, I'd guess that it's very sugary so it's a good conductor (absorbs microwave energy well) and quite viscous (so it doesn't conduct energy away from that spot very well). Some localised patches of it are being superheated to steam, which briefly flashes into a plasma.

On preview: I bet it's the diced shallots in the sauce. They sound perfect for the process described in my second link as they're about the right size and juicy.

Note: IANAPhysicist. Hopefully someone will be along to correct me soon.

As regards the non-microwave-safe plastic, there seems to be some controversy. Some people worry that heating some plastics can lead to the release of unpleasant chemicals into the food, although I've read trustworthy sources saying that this isn't true. It mostly seems to be a USA-specific concern, as all the microwave-ware I've seen for sale in the UK and around Europe are plastics, and people seem happy. The biggest concern is simply that the plastic can't stand the temperature of the heated food, and will melt / deform in the microwave. In any event, it can't be responsible for arcing, unless it's coated with a metallic paint or something similar.
posted by metaBugs at 7:25 PM on December 11, 2009 [11 favorites]

It's too small. Put a cup of water in with it.
posted by weapons-grade pandemonium at 7:34 PM on December 11, 2009

To clarify: anything polar (so including fats, water, etc) can absorb energy from microwaves, but better electrical conductors absorb the energy more efficiently. So salty or sugary water will absorb energy faster than pure water. Ice is a terrible conductor, which is why it takes so long to melt in the microwave. (So when you're defrosting food, the frozen parts are absorbing energy really slowly and the thawed parts are absorbing it much quicker, which is why you get some bits completely and rapidly cooked while others are still frozen: that thawed 10% of the chicken breast was absorbing 90% of the total energy in the microwave).

Pure water can also lose energy very efficiently (by boiling, or by spreading the energy throughout the whole jar of water by convection), slowing or preventing the buildup of enough energy to form a plasma. So in situations where you have a good conductor trapped in a small area (e.g. the sugary juices in a grape, or a relatively viscous sugary/salty sauce) energy builds up very fast but is dissappated very slowly. So in some patches it's much easier to reach that critical point.
posted by metaBugs at 7:38 PM on December 11, 2009 [2 favorites]

metaBugs, that was a terrific explanation of what's going on.

I dug the cup out of the trash and rinsed all the sauce remnants out. Looking closely, I can see a short raised line etched into the plastic that I'm guessing is from the mini-lightning striking the cup while the carousel was turning. I will resist the urge to burn another line into the cup investigate that further tonight.
posted by emelenjr at 7:59 PM on December 11, 2009

Seconding WGP. Run the microwave empty and you'll see the same behavior.
posted by Lazlo at 11:53 PM on December 11, 2009

It's too small. Put a cup of water in with it.

That.
posted by SLC Mom at 12:05 AM on December 12, 2009

Perhaps your dumplings are arcing in much the same manner as a grape. Are they stuffed?
posted by Muirwylde at 11:05 PM on December 13, 2009