Preheat oven for 10 minutes at 400 degrees

I saw this in a recipe the other day, and it struck me as a rather old-fashioned instruction, though I wonder if it really is. What I see most often in recipes these days is "Preheat oven to ..." And yet the "Preheat oven for x minutes at ..." did not strike me as particularly odd, and I wonder if it's because this is the way recipes used to give preheating instructions.

Is there some practical reason why preheating an oven for 10 minutes at a given temperature is different than just preheating to that temperature? For what it's worth, I'm using my mom's old reliable Kenmore oven, which is at least 25 years old.

Katie wrote:Is there some practical reason why preheating an oven for 10 minutes at a given temperature is different than just preheating to that temperature? For what it's worth, I'm using my mom's old reliable Kenmore oven, which is at least 25 years old.

I think the assumption probably is that it takes about 10 minutes for an oven to actually get up to the temperature set on the dial.

Hi,

Preheating your oven for 15 minutes will assure you have really reached a uniform temperature. While it may not be specifically stated, it is understood you preheat the oven for 10-15 minutes before use.

I recently had my three year old oven recalibrated. The serviceman had a mercury thermometer in the center of the oven. After some minutes, the oven made the beep it had reached temperature. We checked the thermometer to find it was still short 50-75 degrees. He said it may be correct temperature wherever the sensor is, but it may not yet have reached temperature in the center. Once we hit 15 minutes, then it had stabilized to uniform temperature. (It was off by 25 degrees, which we then recalibrated the oven)

Once properly heated, then your baked goods timing will be fairly reliable.

Regards,

Remembering that we talked about this before, I come back to ask about a recipe instruction I saw today, and about the general practice of beginning oven-based recipes with a preheating instruction.

Here's how a recipe for vegetable (zucchini/eggplant) lasagna that I saw today begins:

"Preheat oven to 500 degrees. Sprinkle 2 tablespoons salt over eggplant slices, and let drain for 45 minutes."

Now, seriously, why should you preheat an oven to 500 degrees 45 minutes before your eggplant slices are done draining and the rest of the lasagna is assembled, which is to say, approaching an hour before you're ready to put the lasagna in the oven? Where's the benefit of using your overabundance of summer zucchini and eggplant in a lasagna dish on a hot day if it requires preheating an oven to 500 degrees a full hour before you're ready to put the lasagna in the oven?

Of course it makes no sense. So why is "Preheat" usually the first word in the recipe for anything cooked inthe oven?

Preheating for longer than it takes to merely come to temp insures that the cooking chamber is well heated through and through and helps the oven maintain a more stable temp while cooking.

Katie wrote:So why is "Preheat" usually the first word in the recipe for anything cooked inthe oven?

Likely because the need to preheat outweighs the minimal wastefulness of keeping the preheated oven waiting for a bit. Putting it after the "wait 45 minutes" doesn't make lots of sense either and putting it in the middle somewhere is awkward. It's a reminder that's necessary and they assume a thoughtful person will adapt accordingly. As for non-thoughtful people*, it's not a serious detriment.

*I had an acquaintance years ago who had no familiarity with driving downtown from the North Side and asked me for the best route to take. I told him and he took detailed notes. He then asked "how do I get back?" I said just reverse the directions. He said "it would be helpful if you could just explain it." He was a college graduate.

It's not so much wasting the gas that concerns me as having an oven come up to 500 degrees within 10 minutes or so and then sit there at 500 degrees for another 50 minutes or so on a hot day in August when I'm running the air conditioning to try to keep the house 20 degrees cooler than it is ouside.

I get your point, by spinynorman99, about recipes needing to be idiot-proof, but I'm not so persuaded by yours, stevez, in this particular case. How big a deal is oven temperature stability that I should have the oven on and empty for an hour or so before putting a dish in? After all, it's not a soufflé, it's just vegetable lasagna. I'm going to "bake until bubbly." Ten extra minutes on the back end if necessary makes more sense to me than 50 extra minutes on the front end.

Of course, it's a common sense thing. But I have a feeling that going forward, I'm going to cast a withering look at recipes that start with "Preheat oven to ..." and proceed to present 30 minutes or more of prep instructions.

Katie wrote:How big a deal is oven temperature stability that I should have the oven on and empty for an hour or so before putting a dish in? After all, it's not a soufflé, it's just vegetable lasagna. I'm going to "bake until bubbly." Ten extra minutes on the back end if necessary makes more sense to me than 50 extra minutes on the front end.

Of course, it's a common sense thing. But I have a feeling that going forward, I'm going to cast a withering look at recipes that start with "Preheat oven to ..." and proceed to present 30 minutes or more of prep instructions.

I agree that if you're making a dish like lasagna or heating up a frozen TV dinner that it's probably not as important to give the oven time to preheat its entire mass to temp, but if you're baking bread or a cake, for example, where even heat leads to a superior product, then it is important. Like you said, common sense should prevail.

Last time I let my oven sit at 500 degrees for an hour, it melted the control module. $150 bucks later, I'm not doing that again.

I like spiney's explanation. There is also quite a bit of variation in how fast an oven will preheat so when would you like a recipe to tell you when to preheat? For instance, I have never had an oven preheat to 500 degrees in 10 minutes. Maybe yours does (unlikely, I suspect it is not actually uniformly heated to 500 degrees), but I have had ovens where it takes half an hour to reach that temperature.

Better to just put it first and have it ready for when the recipe finally uses the oven.

HI,

Recently with this hot weather, I use my oven quite reluctantly.

I made childhood favorite porcupines. Instead of preheating the oven, I decided to put them in and then turn on the oven. I knew I would need to leave them in longer. It really did not work out all that well. They ended up really needing more time than I even expected.

The 10 minutes to at least reach temperature prior to commencing cooking is time well spent.

***

When I bake pies, I usually bake them on the bottom slot. I have a heavy cookie sheet resting on top the shelf. This does require extra time for preheating, so I do go about 30 minutes.

Regards,
Cathy2

I like to kill two birds with one stone so I slap a coat of flaxseed oil on my cast iron pans to season them and fire up the oven for whatever I'm baking and get both done at the same time.

baking bread tonight so I'll do just that....

mhill95149 wrote:I like to kill two birds with one stone so I slap a coat of flaxseed oil on my cast iron pans to season them and fire up the oven for whatever I'm baking and get both done at the same time.

baking bread tonight so I'll do just that....

GReat idea!

I agree about the cast-iron pans, great idea.

I don't really know how long it takes my oven to heat up to 500 degrees, but it does beep at me when it gets there, so I'll have to record the times for a few preheating temperatures for future reference. I personally see no point in a preheating time longer than the time required to come up to temperature, i.e., the time to the beep, but then I'm not baking breads or other such sensitive items. I also know from experience that my oven runs hot; required cooking times at the specified temperature are always at the low end of the range of recommended cooking times if not below the lower end of the range.