Fiber plate used inside a microwave oven

Do you mean the little plate (Usually in one of the top corners) which the microwaves go through to get into the main chamber of the oven? If so, then the answer is self evident...
Del

There is a difference between self evident and obvious.
I do agree with your comment about the Prof's who say such stuff.
I once stood up at Uni after a lecturer declined to explain something and said..
'If anyone DID understand that please raise your hand'...
Cunningly wording it, as I knew no-one would have the bottle to raise a hand.

But do me a favour...I explain it in the previous sentence.
If one's attention span and ability to recall information can't straddle a full stop then I despair.
It is 'self evident' was just a short hand (and pretentious) way of saying...
"If the assertion of my previous sentence is true, then that sentence actually explains the answer".

If you want a pop at me and you think you are hard enough, just bring it on
...I've had a tough couple of weeks an I'm in the mood for a fight
...So be nice else I'll hisss and spit and puke on your carpet.
Del

Now now, there is no need to be catty...

um, its not magnetic?

I've never seen a fiber plate here in the US. Only glass and, usually, they re made of Pyrex.

The use of any metallic medium inside a microwave, even aluminum foil, would likely do damage to the microwave unit. Even a simple utensil, like a kitchen fork, will often cause a shower of sparks, not because of it's shape but because it's made of metal.

L.J.

OOoops --- "The use of any metallic medium inside a microwave, even aluminum foil, would likely do damage to the microwave unit."

Posts 4 & 8 are on the right track. Wiki , too , does a pretty good job of explaining how (most) metals react inside a 'waver'... [scroll to near bottom and read: "Microwaving food containing an individual smooth metal object without pointed ends (for example, a spoon) usually does not produce sparking." ]

IT ALL depends. I have probably NEVER put soup, Ramen noodles, or leftovers into my mw oven WITHOUT either a spoon OR a fork in it ... thousands of times, with NO sparking whatsoever.

By the same token, during an Arby's sandwich re-heating episode ... ((they use the wrapping material that is thin foil laminated with thin paper)) ... I opened the foil, leaving the sandwich on top, exposed, but with several "folds" at the edges of the foil-paper.

About four seconds on Hi power, and the foil sparked spectacularly, even flaring a small flame or two (self-extinguished).

T H A T won't be going in, ever again...! We live and learn, eh?

Apparently, MY forks have just the right length and spacing of tines so as to be safe (in THIS oven, anyway). Spoons are rarely a problem, as noted both in the Wiki article and HERE.

[excerpt] "Put a fork in the microwave and you may get sparks between the tines. Put a heavy ice cream spoon in and you'll get current and heat, but no light show - there's no convenient place for the spoon to arc to and a heavy ice cream spoon usually has enough metal to carry the current without heating up too much."

Each different oven will exhibit its own characteristics with different metals.

There is no "universal" judgement, here. {except 'maybe' the arby's-type wrappers}

Our maid generated enough arcs with forks to destroy the 'fiber' plate which seems to have a lot of mica in it. I got it replaced. Next problem is that the paint on the surface of the tray that rotates (carousel?) is chipped off in one or two places. Could someone advise me on the specs of the paint and whether or not it should be baked after re-painting? If I left convection on for one hour, say at 150-180F, would that suffice for baking the paint? After all it is an oven!

I think you'll find that tray is glazed, not painted, for use in a convection microwave oven. I doubt if you'll have much luck with paint. Anyone that knows better, please correct me!

The fibre plate is a cover over the opening from where the microwaves are generated by the magnetron (inside the outer cover, but outside the internal oven space).

Obviously it cannot be metal or the microwaves would not be able to enter the food space in the oven.

You can actually put metal in the oven, because it is possible to heat say, a store bought pie in an aluminium foil pie tray. Some operating instructions will explain this. However you cannot use the tray if the foil extends too far outside the food item, or too high above the food etc. But it is quite safe to do as long as no "spark showers" start.

Tony

Metal is occasionally used for wraps on foods like "Hot Pockets" to crisp the outside. Its on the back side of the paper. Somebody spent a lot of time and effort getting it right though. You CAN blow a magnatron when you put metal in the oven.

I havent figured out the relationship to hairballs yet.

okay I guess I'll weigh in on this. I seriously doubt any amount of metal in a microwave will cause the magnetron to blow up, overheat or otherwise fail. The reason you get arcs and sparks on your fork is probably due to the fork acting as an antenna. The forks are spaced adequately apart to cause a momentary difference in potential as the microwaves are absorbed. The spoon does not arc simply because there is no difference in potential. Try doing this. put an old CD in the microwave, something you don't want. Watch what happens. as the current induced by the microwaves melts and parts the very thin layer of metal in the CD it will be begin to arc over and cause a shower of sparks in a random pattern across the CD. I'm just guessing but i think conventional wisdom tells you not to put a pan, or other metalic object in the microwave because it will absorb a disproportionately large amount of energy and the food won't heat (but the container will). The same thing happens with an unsually dense coffee mug... ever notice how the handle is hotter than the water when you go to pick it up? Anyways, someone please weigh in on this with more knowledge than me, this is all just a pet theory of mine, nothing scientific.

Since the whole point of the device is to put energy into moisture, if something has no water content, the energy has no place to go. As someone else suggested, if there's a lot of moisture in the area, the moisture will get heated and not enough residual microwaves will be available to arc.

I seriously doubt there is a hard and fast rule here but given the general ignorance of some people, it's safer to put a "speed limit" of sorts in its use. I can, for example, heat potatoes very fast by inserting a clean aluminum spike into one end and driving it all the way in. Cuts the cooking time in half but I'd never suggest that to my mom. I love her a lot but mom has a way of taking "fool proof" devices and making them self destruct.

What I'd like to know is why the guys (and gals) who design microwaves can't have the turntable stop where it started? A super hot cup of coffee will stop with the handle inside. Why?

L.J.

I often use the microwave to heat a plate that I'm about to use for a meal. It warms up nicely in about 1 minute but, although I understand that the microwaves heat moisture, it's hard to see where this moisture would be in a glazed ceramic plate.

Water is indeed the normal energy absorber in most foods. About 50 years ago I was life-testing microwave ovens, and put some slices of bacon on paper towels in an oven that also had slowly flowing water in a closed (except for input and output tubes) glass container to carry away most of the energy. We monitored the flow and temperature change of the water to track the output of the unit. At the end of an 8-hour shift, I ate nice crisp, just warm bacon. Once the water had been driven out of the bacon, it essentially stopped heating.

Ceramic materials vary greatly in their transparency to microwaves. It seems (anecdotal observations only - no really scientific investigation) that high quality ceramics (usually white to translucent and commonly quite thin) are transparent to microwaves, as they are (almost) to light. They heat up very little if at all, other than indirectly from the food. As the ceramics get cheaper, they generally get darker in color (absorb more light), and have to be thicker for strength, so absorb more still. As they absorb more light, they also seem to absorb more microwaves. Once you get to earthenware (bottom end of the quality scale), it absorbs so much that there is significant danger of cracking the pot.

You must be using a medium quality ceramic, so it does heat, but doesn't crack.

Sometimes, food is intentionally packaged with some non-water microwave absorber to increase the temperature, as is the case with the gray stuff on the bottom of microwave-pop-corn bags.

stoneware and crockery (made from fired clay) has a lot of water bound up chemically in the matrix of the ceramic (not unlike concrete does.). but porcelain (bone china) is actually a translucent glass and does not have water bound up in the matrix, so it does not heat up.

Sounds reasonable!

I've just watched an interesting programme called 'Bang Goes the Theory' (recorded on Monday). In one of the items the presenter explained that microwaves will try to excite the molecules in any material but will be most successful with liquids, where the molecules are free to move and least successful in solids, where the molecules are bound together.

This was demonstrated by showing a glass bottle being microwaved for a long period without getting appreciably warmer. A glass rod was then heated at one end using a blowtorch until the end of the rod glowed. This rod was then dropped into the bottle, hot end up, & the bottle replaced in the microwave. The end of the rod got visibly hotter & then started to melt the bottle.

WOW, That is interesting! Was that on the BBC? I don't watch TV much, but I'd like to see that one...

BBC1 Mondays, 7:30 I think but the item about the microwave has made it to You Tube.

Thanks, but

(I'm in the USA)

As to stopping the turntable where you want, just time the revolution and set your cook time a multiple of that. Ours is 6 rpm. Therefore if I am heating something for 30 seconds, it ends up in the same position that it started. If I heat for 15 seconds I set it on the back of the turntable. Of course I never use those numbers. 11, 22, 44, 66, 99, those are the times I use. ...then of course I end up doing math to decide where to set the bowl.

Ok, maybe Blow up was too strong of a description, But if you think any transmitter-klystron, magnatron , transistor, etc can't be damaged by standing waves, which are always produced by improper loading, you'd better think again.

We used to have pretty big magnetrons on old radars. They did not blow up under any circumstances. After prolonged use they just declined there radiated output. Change the magnetron and the radar / microwave is as good as new.

Laughing Jaguar - my micro plate revolves 1 revolution in 10 sec. on the display

Therefore I set the time for coffee at 100 (sec.) this results in the handle comming

back to the front when the plate has made exactly 10 revolutions. A similiar method

obviously can be used for your micro depending on the timing of the plate.