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ptjw7uk
09-08-2012, 03:14 PM
A bit OT but I thought I wpould ask the font of all knowledge.
The other day I was going to heat some milk in a mug and remembered the last time I did it the mug got to hot to handle.... thinks put milk in plastic jug!! Did that and put in micrwave, turned it on and flash and bangs with arcing at the grill aperture of the unit.
Opened door put milk in another jug turned it on OK --Hot milk.
Soooo why did it not like th eplastic jug, it just seems to be polythene, a measuring jug! Nowt specisl!

Any answers

Peter

dfw5914
09-08-2012, 04:40 PM
What color was the plastic? Possibly a metalic component in the coloring agent.

winchman
09-08-2012, 04:52 PM
Hormel puts their side dishes in plastic containers that can be microwaved, but there's a statement in the instructions that says, "Do not use container for reheating product." I recently wrote to their customer service asking why the container shouldn't be used for reheating. They replied that it's only designed for heating the product one time.

What could possibly limit the use of a microwavable container to one cycle?

Since I can't die young any more, I'll just continue to reheat the leftovers in the containers like I've been doing for years. Eating their stuff will probably kill me before reheating it in the containers will.

darryl
09-08-2012, 05:15 PM
A nuker works by activating water molecules- in other words it's the moisture content that absorbs the energy, consequently getting hot. If it begins to steam, the steam becomes the first thing in the path of the microwaves to absorb the energy. The steam is above the food and in contact with the sides of the container. There is no limit to how hot the steam will get, and it can easily heat the plastic to its forming temperature and beyond. Because the plastic is generally very light it will heat quickly. You can easily have a situation where the food is still cool but the container has become heated and mis-shaped above the level of the food. Not something you'd really want to have when you're expecting to eat the product which is in close contact with the container. Generally you'd toss the container after this has happened, since it probably won't seal anymore. I don't think there's really a health hazard to re-using it to heat food again, and I also don't think the plastic will have changed to something that's less than food grade, although you can imagine that if you really over heat and discolor it- well I wouldn't use a burnt cup to drink water from, etc.

Mike Amick
09-08-2012, 09:37 PM
+1 for dfw5914

Probably what he said or .. even actual metallic paint on graphic on mug.

You can actually put metal in a microwave .. it just can't be exposed. It has to be
covered .. like in a paper bag type thing.

JoeLee
09-08-2012, 09:44 PM
+1 for dfw5914

Probably what he said or .. even actual metallic paint on graphic on mug.

You can actually put metal in a microwave .. it just can't be exposed. It has to be
covered .. like in a paper bag type thing.

I never knew that!!! What does the paper bag have to do with it?? It's RF invisible. It doesn't block the RF.

JL..............

J Tiers
09-08-2012, 09:51 PM
It's lossy, maybe, although I don't "buy" the whole thing of paper directly. Maybe it absorbs steam and the moisture in it does the absorption.

I am fairly sure that one of the microwaves we had required the glass tray..... because the tray was just lossy enough to keep the standing wave ratio down to where the power tube could handle it.

Metal itself isn't so much the issue, the whole inside of the cooking cavity is made of metal. The issues include thin metal which may heat and melt (the gold on your fancy plates), or metal with gaps which may act as antennas and arc at the ends.... That sort of thing

Grind Hard
09-08-2012, 10:45 PM
Ok this is what my brother tells me, he's an expert in plastic-stuff:

"Companies are using highly oriented plastic sheeting now for thermoformed containers. Basically the resin is extruded through a die, then stretched in a series of rollers then pulled in an oven. This results in a high degree of molecular orientation. The result is they can use thinner (less) material for an application without giving up strength.

In theory the heat radiated from the food in your container could relax the molecules and cause them to de-orient (warp and shrink and distort) resulting in spilled food or beverage. This is why they suggest only one use per container. In reality so long as you don't overheat the container you should get a few uses out of it."

ptjw7uk
09-09-2012, 03:23 AM
The jug is semi clear, milky in appearance, almost see through it.
On the bottom is one of those recycle triangles with a 5 in the middle and 'PP' under it.
It also says made in china on it so I think it could be anything!!!

The mug is stoneware with 'Computer Whizz' on the side the grand kids bought it for me last xmas. So I suppose it could have a metallic glaze on that!

Peter

JoeLee
09-09-2012, 08:19 AM
Well, I don't know if I buy the paper bag deal but I do know from experience that anything metal can cause arcing. Years ago while visiting my aunt I put a dish in her microwave, the dish was an old family relic which was decorated with gold leaf lines and designs all over it. As soon as I hit the start button it was like the forth of July for a few seconds, arcing danced all over the plate, then it was over. All the gold leaf was burnt to a frazzle. Boy was she pissed at me!

JL....................

darryl
09-09-2012, 02:16 PM
Here we go again- fun with microwave ovens- ever put a CD in a microwave? You can do almost anything in a m/o for a few seconds- the tubes are pretty rugged. I've never damaged one anyway. The CD looks pretty cool afterwards. Some ventilation would be a good idea :)

A.K. Boomer
09-09-2012, 07:47 PM
He did say measuring cup so the first thing that came to my mind was the print,
wonder if it still looks the same - could be metalic paint in the print or maybe it's some of that chinese leaded plastic.:p

Paul Alciatore
09-09-2012, 10:47 PM
I have used a plastic measuring cup in the microwave to heat water for instant coffee for years. No problems. YMMV.

As for the paper absorbing or moderating things a bit, I would have said "No way!" as late as the middle of last week, but something happened a couple of mornings ago. I have been cooking turkey bacon in my oldest microwave every morning for several years now and I thought I had it down to a science. Paper plate, paper towel, three strips of bacon, cover with another paper towel. In microwave for 2:33 at full power with the rotation on. It always comes out perfect, well cooked and crisp. Well, two days ago I did just that and the bacon was half black. Burnt to a crisp. I tried a second batch and it too started to burn. Only a fast finger on the Off button saved it. But why? Well, I noticed that the double layer of paper towel that we normally leave on the rotating tray was absent. We do this to make clean-up easier. Apparently someone took it out and did not replace it.

The next morning I replaced the paper towel and used my original technique and time and got perfect bacon again. With everything else exactly the same, two layers of paper towel under my paper plate made the difference between burnt and perfectly cooked turkey bacon. So there must be something to using paper to moderate microwaves. And perhaps even a single layer of paper will have a profound effect.

darryl
09-10-2012, 12:57 AM
Well, let's try to reason this one out. If the paper was absorbing a significant amount of energy, it would be getting hot and burning. The moisture content in the paper has to be very low, otherwise the paper would be heavy. It's not- it's as light as- paper. It's not absorbing near enough energy to rob something else in there of energy. If it's been in there for some time, it should be bone dry. If the moisture content has something to do with things, the 'moderating' effects of the paper should disappear in short order. This doesn't seem to be the case with cooking the bacon, so the paper must be causing something else to be absorbing a significant part of the energy and keeping it away from the bacon. Could it be acting somewhat like the ionosphere, trapping energy between itself and the bottom of the oven? Could it be diffusing the energy, thus helping to eliminate hot spots within the oven? Maybe the plate is getting hotter than it might without the paper, but I think you'd notice that. Maybe with only a few minutes run time, it's not something that would make itself apparent. A with paper and a without paper temperature measurement of the plate would be a good place to start. You might also check the temperature of the walls, roof and floor.

With these temperature measurements, you'll find out if the microwave energy is going into something else besides the food. One thing that would be hard to put a handle to is if the tube itself is being made to absorb some of the 'back wave'. It's not going to be easy to monitor the temperature at the actual tube.

EVguru
09-10-2012, 06:27 AM
Not directly related, but did you know you can melt glass in a microwave?


Normally, the molecules in glass are too 'rigid' to be excited by the microwaves, but if you heat the glass to the point at which it becomes plastic, they can absorb microwaves.

If you place a blob of molten glass on the top of a glass bottle and then microwave it, you can melt the whole bottle.

JoeLee
09-10-2012, 08:17 AM
I have used a plastic measuring cup in the microwave to heat water for instant coffee for years. No problems. YMMV.

As for the paper absorbing or moderating things a bit, I would have said "No way!" as late as the middle of last week, but something happened a couple of mornings ago. I have been cooking turkey bacon in my oldest microwave every morning for several years now and I thought I had it down to a science. Paper plate, paper towel, three strips of bacon, cover with another paper towel. In microwave for 2:33 at full power with the rotation on. It always comes out perfect, well cooked and crisp. Well, two days ago I did just that and the bacon was half black. Burnt to a crisp. I tried a second batch and it too started to burn. Only a fast finger on the Off button saved it. But why? Well, I noticed that the double layer of paper towel that we normally leave on the rotating tray was absent. We do this to make clean-up easier. Apparently someone took it out and did not replace it.

The next morning I replaced the paper towel and used my original technique and time and got perfect bacon again. With everything else exactly the same, two layers of paper towel under my paper plate made the difference between burnt and perfectly cooked turkey bacon. So there must be something to using paper to moderate microwaves. And perhaps even a single layer of paper will have a profound effect.

Perhaps the double layer of paper towels you usually have under the paper plate acted as an insulation blanket between the paper dish and the glass tray of the microwave. With out two paper towels under the dish the heat from the sizzling hot bacon conducted at a faster rate to the glass tray causing faster cooking and burning.

JL.................

A.K. Boomer
09-10-2012, 09:43 AM
Not directly related, but did you know you can melt glass in a microwave?


Normally, the molecules in glass are too 'rigid' to be excited by the microwaves, but if you heat the glass to the point at which it becomes plastic, they can absorb microwaves.

If you place a blob of molten glass on the top of a glass bottle and then microwave it, you can melt the whole bottle.


That's crazy - wonder who found that out and how? - was it just some guy experimenting with things like blowing up gremlins and such and decided to try molten glass or maybe someone with a working theory ? Hmmm

I don't use microwave ovens for all kinds of reasons but mainly because I try to avoid applying heat to my food, in that respect they are very very bad for you...:)