Microwave cooking times

[Keeping Up]

This is defintely my first topic in this area of the Forum! I should know the answer to this - but I don't. And I did contemplate posting it in the Electrical areas, but decided I'd try here first so I can get a real answer instead of a mathematical treatise on the theory of microwaves.

 

I have a packet in front of me, that I have just taken out of the freezer. The instructions say "microwave from frozen, 3 minutes" for my size microwave. OK, I think I can cope with that. Or can I. The problem is, I want to cook two of them. Now of course I could cook one for 3 minutes, then cook the other one for 3 minutes, but that seems ridiculous. Surely I can cook them both at the same time. But how long should I cook them for. 3 minutes? 6 minutes? Or maybe 4 minutes and 30 seconds? I really don't know.

 

Maybe I'll do them in the ordinary oven instead, at least the cooking time is much the same whether there are 1 or 2 things in there, but I'll have to wait for the oven to heat up, and then it takes forever to cook.

 

Does anybody know the answer please?

[Guest]

Half the time again for the second one. e.g. 3 mins for one, and 4 mins 30secs for two.

 

ps your microwave consumes twice as many watts as its cooking power

[journeyperson]

This is defintely my first topic in this area of the Forum! I should know the answer to this - but I don't. And I did contemplate posting it in the Electrical areas, but decided I'd try here first so I can get a real answer instead of a mathematical treatise on the theory of microwaves.

 

I have a packet in front of me, that I have just taken out of the freezer. The instructions say "microwave from frozen, 3 minutes" for my size microwave. OK, I think I can cope with that. Or can I. The problem is, I want to cook two of them. Now of course I could cook one for 3 minutes, then cook the other one for 3 minutes, but that seems ridiculous. Surely I can cook them both at the same time. But how long should I cook them for. 3 minutes? 6 minutes? Or maybe 4 minutes and 30 seconds? I really don't know.

 

Maybe I'll do them in the ordinary oven instead, at least the cooking time is much the same whether there are 1 or 2 things in there, but I'll have to wait for the oven to heat up, and then it takes forever to cook.

 

Does anybody know the answer please?

 

Even if the cooking time was double you could be eating it by now! I have this image of you sitting there with your stomach rumbling, waiting for a reply. Try it for 4 mins 30 secs

[Guest]

Well, have you cooked it yet Allan? Was it good?

[Keeping Up]

No I didn't wait for a reply, and I did it for 4m30s like I usually would. No idea why except that intuitively it "feels" that the time should be increased but doubling it "feels" like it's too long. It was hot, and tasty, but I'd still be interested to know if there's any way of knowing exactly how much extra time to add, not just for 2 portions but 3 or 4 - and likewise if the packet says "5 minutes" but I really don't want 10 portions of peas so how long for one portion?

 

And thanks Catweasel for reminding me to double the power (plus the extra that needs to be put back into the batteries and not forgetting the Puke-Up effect of too many currants)

Edited March 8, 2009 by Keeping Up

[Gibbo]

Microwave cooking time for additional items is (total number of packets)^0.6 * cooking time for one packet

 

The reason is that the wavelength of the microwaves.............

 

B*ll*xs

 

I have no idea why but it works. I found it on a cooking website.

 

Gibbo

[Ex- Member]

Microwave meals suck, do some proper cooking and don't be so bone idle

[Keeping Up]

Thanks Gibbo

 

Now I can derive the formula for cooking "B" portions when the cooking time is quoted for "ll" portions using a microwave of wattage "x" and size "s" - oh you've already given me the formula "B*ll*xs"

 

Microwave meals suck, do some proper cooking and don't be so bone idle

I agree - that's what I normally do, which is why I didn't know the cooking times for microwaves (I could have prepared the same item and cooked it in the oven, and already known the cooking times, but it would have taken lots longer)

[chris w]

From a physics point of view, the magnetron delivers a constant amount of microwave power to the oven cavity. That power will be absorbed by the product(s) to be cooked. All things being equal, if two equal sized packs of peas are placed symetrically in the microwave they will each absorb half of the available microwave power and therefore heat up by the same amount. So I would reckon that the cooking of two portions of a product needs double the microwave time of one product.

 

This differs from a conventional oven in that, in the latter, there is an excess of "heat" and even several portions of the same product will not absorb all the heat available.

 

Chris

Edited March 9, 2009 by chris w

[bottle]

Theory correct, reality differs.

[Gibbo]

Theory correct, reality differs.

 

Indeed.

 

The reason it differs is that any microwaves that aren't absorbed by food have to go somewhere. They can't just dissappear. Where do they go? They go back up into the magnetron (where they came from), set up standing waves in there and reduce the efficiency of the magnetron thus it actually kicks out less RF. The more food goes into the oven, the more efficiently the magnetron kicks out microwaves. Which is why doubling the amount of food in the microwave does not require a doubling of cooking time.

 

Gibbo

[alan_fincher]

From a physics point of view, the magnetron delivers a constant amount of microwave power to the oven cavity. That power will be absorbed by the product(s) to be cooked. All things being equal, if two equal sized packs of peas are placed symetrically in the microwave they will each absorb half of the available microwave power and therefore heat up by the same amount. So I would reckon that the cooking of two portions of a product needs double the microwave time of one product.

 

This differs from a conventional oven in that, in the latter, there is an excess of "heat" and even several portions of the same product will not absorb all the heat available.

 

Chris

So if it's just a case of the energy the magnetron produces being "sucked up" by the food, and if it takes a set amount of energy to cook or heat the food, why when you look at the packaging is the cooking time at 600 watts never 1.5 times the cooking time at 900 watts, (or even anything close to ?).

 

If we can answer this one in less than 3 pages, gentlemen, I may just be able to keep up!

[Barry]

Well my money's on Gibbo at the minute

[Keeping Up]

Certainly I know, and my wife has frequently proved it, that doubling the cooking time will produce only a blackened and inedible mess.

Of course, she can do that in a conventional oven too.

[alan_fincher]

Certainly I know, and my wife has frequently proved it, that doubling the cooking time will produce only a blackened and inedible mess.

Of course, she can do that in a conventional oven too.

A "take away" this evening, then, is it, Allan ?

[Gibbo]

Well I just tried it whilst eating my "elevensies"

 

1 cup of water. Start temperature 17.1 deg C. 1 minute on full power. Stirr, end temperature 56.0 deg C

 

2 cups of water (same size). Start temperature 17.1 deg C. 2 minutes on full power. Stirr, end temperature 67 deg C

 

Doubling the food volume does not require double the cooking time.

 

But we already knew that so why did I bother?

 

Gibbo

[Keeping Up]

Well I just tried it whilst eating my "elevensies"

 

1 cup of water. Start temperature 17.1 deg C. 1 minute on full power. Stirr, end temperature 56.0 deg C

 

2 cups of water (same size). Start temperature 17.1 deg C. 2 minutes on full power. Stirr, end temperature 67 deg C

 

Doubling the food volume does not require double the cooking time.

 

But we already knew that so why did I bother?

 

Gibbo

Brilliant

 

Your tests show that a time of 1 minute 33 seconds would have brought your two cups up to the same temperature as the first. The formula you found in the cookbook suggests a time of 1 minute 31 seconds.

 

That's near enough for me - and translates as "just add half as much extra" which even Pingu should be able to remember

Edited March 9, 2009 by Keeping Up

[Gibbo]

Brilliant

 

Your tests show that a time of 1 minute 33 seconds would have brought your two cups up to the same temperature as the first. The formula you found in the cookbook suggests a time of 1 minute 31 seconds.

 

That's near enough for me - and translates as "just add half as much extra" which even Pingu should be able to remember

 

I didn't even bother looking to see if it agreed. I knew somene else would do the sums for me

 

Gibbo