Stainless in microwave

[supersurgilator]

I was looking at new microwaves the other day and found one that was all stainless steel inside. How is it that this doesn't cause sparking when the interior of the oven is made out of it, but if you put a piece of metal in there, it would spark. Just wondering!

 

[toggleswitch2]

Metals reflect microwaves preventing their passage. Ditto painted metal. You will notice that micorwave oven racks (meatal) use insulted holders/brackets to keep them away from the walls of the unit.

Technically one can use metal pans up to 1" (2.54 cm) deep in which to cook food, but it has to be far enough away from the walls to prevent arcing. The overall theme is there must be somewhere for the microwaves to go or else one burns out their magnetron.

Instructions say "don't" rather than "OK if..."
I remember early microwaver cookbooks used to say it was ok to put aluminum foil over the bone end of a chicken drumstick to keep it from cooking. Not anymore.

 

[toggleswitch2]

LOL insulated, no insulted.

 

[sudsmaster]

Actually my 2000 Panasonic MW manual says it's ok to cover the ends of poultry limbs with foil... but I've never tried it.

Recently I did try to warm a bottle of USP mineral oil (for seasoning the cutting board on top of a vintage DW), in my Kenmore. It didn't get warm and when the machine started arcing I quickly shut it off. No apparent damage occurred, as I was able to heat a cup of water afterwards OK.

Anyway, yeah, the interior of most microwaves is enamel or powder coated painted sheet steel, not that different in terms of conductivity than stainless steel. If you clean up splatters as soon as they occur I don't see much if any advantage to the SS interiors - and they may even be harder to keep clean than a good powder coated surface.

 

[iheartmaytag]

The advantages to Stainless

It shines, and it's purddy.

 

[toggleswitch2]

Interesting. a nuker works by vilently "shaking" the water molcules to generate friction and heat. I guess oil has no water wtihin! *LOL*

But I'm confused in that fat within meats attracts microwave enregy which is why hamburgers and metballs, etc. cook so well; the microwave enrgy is distributed evenly. Is water a component of fat?

Man oh man If I could invent a pill to change body fat to water...........

 

[supersurgilator]

Yeah our Sharp manual says the same thing. Foil can be used as a shielding agent on areas that are overcooking. Although it usually refers to this when defrosting meats, so maybe on 100% power it would be different.

 

[mielabor]

Water molecules are not the only molecules that absorb microwave energy, fat and some other materials will do the same. No magic fat > water conversion here.

 

[petek]

Not that most people want to but you can cook things like tv dinners in foil trays in the mw but they won't cook as fast, only from the top. So long as the amount of food and its surface area is greater than the metal you're usually ok.

Danby makes a great little MW with a full SS interior and it sells for a mere $79-$89 at Walmart here. One of the few SS oven interiors and exterior available and at such a cheap price.

 

[countryguy]

I have a GE microwave and it has 2 metal full width racks. I always wondered also why it would have metal racks when I had always heard never to put anything metallic in the oven.

Gary

 

[iheartmaytag]

Sugar

Will absorb microwave energy very rapidly. I make peanut brittle in the microwavy 10 minutes start to finish with pauses to stir.

You can try the sugar theroy with a jelly dounut. It will take about 20 seconds to liquify.

 

[DADoES]

I microwaved foil-tray TV dinners (back when they were in foil trays) for with no ill effect.

 

[sudsmaster]

OK, the microwave heats water by exciting the bonds between the oxygen atom and the hydrogen atoms in the water molecule.

Natural fats and oils contain O-H bonds in the glycerol portion of the fat molecule.

A mineral oil by definition would not contain any glycerol, so that might explain the absence of heating of a pure mineral oil.

But at this point I'm going to have to review microwave theory and get back to you.

 

[sudsmaster]

Probably a better explanation than I gave

ow Do Microwaves Heat Food?

Microwave heating works by heating the water in foods. The frequency used in microwave ovens optimally heats water molecules. The microwave energy is converted into heat energy of the water molecules, which in turn heat the other molecules in the food. That is why dry foods such as rice and pasta will not cook in a microwave unless they are in some water.

How does microwave heating affect water? A water molecule consists of three atoms: Two hydrogen atoms and one oxygen atom. These atoms share their electrons in such a way that the positive charges are on one side of the water molecule and the negative charges are on the other side. Chemists call this a polar molecule. Water molecules are polar molecules.

Like charges repel each other and unlike charges attract. This happens because the charges each create their own electric fields and each electric field exerts a force on the other particle. Because microwaves are electromagnetic waves they produce constantly changing electric fields in the food inside the microwave oven. The water molecules in the food react to the electric field by rotating to minimize the force on both the positive and negative ends of the molecule. When the electric field changes from positive to negative, as it does with an electromagnetic wave, the water molecules rotate again and orient themselves in the opposite direction.

In ice the molecules can not rotate as easily, so microwaves do not heat ice as effectively as they heat liquid water. The heated liquid water must heat the frozen water by normal conduction. So frozen foods can heat unevenly.

The 2.45 gigahertz frequency works in microwave ovens because the time it takes for the electromagnetic wave to change the electric field from positive to negative is just the right amount of time for the water molecules to rotate. Hence the water molecules can rotate at the fastest possible rate. In addition, this frequency is not used for communications, so microwave ovens won't interfere with cell phones, televisions, and so forth.
Why do Rotating Water Molecules Heat Food?

The answer has to do with the nature of heat energy and temperature. Heat energy is the random kinetic energy (energy of motion) of the individual atoms and molecules. When something is hotter, the atoms and molecules are randomly moving around more rapidly. As the temperature decreases, the atoms and molecules move more slowly.

As the water molecules rotate, they bump other molecules causing them to begin moving randomly. The process is like frictional heating. Microwave energy converts to heat energy by causing the molecules in food to increase the speed of their random motions.

Your meal gets nice and hot.

http://physics.suite101.com/article.cfm/how_do_microwave_ovens_work

 

[washerboy]

flaming cookies

I attempted to bake cookies in my microwave once..after it cooled down from the flames I put it in the trash and got a new one the next day. If your wondering.. cookies dont bake in microwaves.

 

[sudsmaster]

Further reading indicates that fat and sugar molecules are also heated by microwave energy, through a similar excitation process, and foods may also be heated by what is called an ionic reaction, where the ions (as in a salt solution) attempt to migrate alternately in the direction of the changing microwave field.

Thus I'll have to back off from my earlier assertion that the H-O bond is specifically excited by microwaves. Although that's what I recall from physics/chemistry/nutrition classes in the 70's, it's not borne out by what I've been able to find on-line so far.

It appears I was more or less correct when I attributed the melting of plastic containers when nuking high fat food to the fact that the fat gets hotter than water, due to the ability of water to stop heating the food when it escapes as steam, whereas the fat or sugar will continue to heat without changing phase, and therefore can become hotter than 212F (the boiling point of water).

 

[toggleswitch2]

flaming cookies

Yes apparently one of the the joys of microwaving is that one goes from "hot" to "on fire" without the the classic and traditional stink and look of burn and browning.

 

[retro-man]

Well when I got one of my first microwaves I put in 3 medium size potatoes to cook. Set the timer for 20 minutes and outside I went to have a cocktail on the deck. Well after about 15 minutes smoke was coming out the back door. Oh shit the potatoes. Ran into the house and it was completely filled with smoke. Turned the exhaust fan on and opened windows and doors. Shut the microwave off and opened the door. There stood the 3 potatoes but a little darker in color. I grabbed a plate and tried to pick one up. I dissolved into dust on the plate. Same with the other 2. They never caught fire but just cooked themselves out. It took a week to get rid of the smell. It reminded me of the same smell in nyc. Always thought the city smelled like burnt potatoes.
Jon

 

[iheartmaytag]

One cup of sugar, one cup of corn syrup and two cups of peanuts will reach hard ball stage in about four minutes on high power.

Remove from oven, stir cook high another four minutes, remove stir in 1tsp of butter, 1 tsp of vanilla return to oven for 2 minutes. Remove add 1tsp soda stir and pour onto a buttered, or greased baking sheet. Cool you have the best peanut brittle you can find.

No water molecules were harmed in the making of this candy.

 

[jeffg]

To answer the original question, this link explains why some metal objects cause sparks and others don't. It has to do with the size and shape of the metal, and whether it reflects microwaves (which is fine) or conducts them (this is what causes heat, sparks and arcing):

http://physics.suite101.com/article.cfm/why_no_metal_in_microwave_ovens

 

[alr2903]

Do Not ever try to melt margarine without saran wrap over your pyrex measuring cup, it's like a mini explosion, you will have to take out the turntable and scrub the whole darn thing. alr2903

 

[supersurgilator]

I think you probably cooked your cookies for too long. I have made cookies in the microwave before with no problem. They only take about 2 minutes per batch. I got a microwave cookbook and there are a lot of cool things in there. I've also done muffins without any problem. You just have to remember that these items don't brown (which could be why you overcooked them).

 

[DADoES]

User lower power levels to ward-off explosions when reheating and melting.

 

[jetcone]

I think the trick

for metal is it has to have no sharp edges or points, if its round or smooth it won't arc in the microwave.
My RR2 has an all SS interior always had. It is nice and shiny!

But my Thermadore Thermatronic oven is low power microwave boost and it can take foil or any metal parts.

 

[toggleswitch2]

~It reminded me of the same smell in nyc. Always thought the city smelled like burnt potatoes.

AHEM! Some of us live in this cesspo.....er place.

*LOL*

 

[mattl]

My microwave has a Sliverstone type interior, everything wipes off easily, nothing sticks, I love it. Worth every penny. It also has cycles for melting butter and chocolate perfectly, as well as melting frozen juice cans and softening ice cream, I use all the cycle often.

It came with a metal pan to brown on and a tall metal rack to raise food up to the dual browners, one Halogen and one infrared. Browns frozen pizza nicely as well as chicken pieces, not hot enough for steaks. I only wish it had a convection feature.

Iheartmaytag, we've been making peanut, actually cashew, brittle for 20 years in the microwave. Always turned out great, except with this oven I had to reduce the times by 30-40%. I forgot this year and followed my recipe and had burned cashew brittle for Christmas. Luckily I had enough stuff to make another batch.