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Large dish of reftrigerated lasagna in an IKEA porcelan dish, enough to serve 10 reasonable adult portions as described here: What would be the best way of preparing lasagne in advance?. The lasagna had been transported for 20 minutes in a cool bag and sat on the worktop for 15 minutes while the oven heated up. The lasagna was placed in the pre-heated fan oven covered in foil at 190C [375F] set to fan with a thin steel tray beneath to catch any overflow.

After ~ 75 minutes, the pasta was barely al-dente, and the cheese on top was not bubbling. There was no classic "Lasagna cooking aroma" in the house. I increased the temp to 220C [430F] and gave it another 30 minutes, with the drip tray removed just in case. By then, the aroma of cooked lasagne was permeating the house and a further 10 minutes without the foil resulted in a perfect, browned lasagna.

When I originally checked the temperature after 75 minutes [with an old round analogue thermometer jam making variety?] the temperature was 45C [115F]. I confirmed this was accurate by touching the probe, it was barely warm. After putting the lasagne back in the oven, I checked the temerature of the drip tray and it was hot, but not so hot that I couldn't place my hand firmly on it.

Much discussion then ensued over an excellent lasagne as whether or not friend's oven was less efficent than mine, broken, or if the fridge-cold lasagne dramatically affected the cooking times.

A frozen lasagne ready meal takes 45 minutes at 180C fan [350F] to heat through, so I suspect my friend's oven is either on the fritz or very inefficent.

With hindsight, a large lasagna will take longer to heat through than a smaller one. I get that, but what is really puzzling is my oven is approximately twice the internal capacity and anything cooked at 190C fan will end up leaning towards cremated rather than raw. The cool drip tray is also puzzling, I'd expect that to have been a lot hotter if I'm honest.

Have I encountered the classic curse of different ovens or am I correct in my assertion that my friend's oven is not working as efficently as it should be? Almost 2 hours to bake a lasaga seems excessive.

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    It sounds like your friend's oven isn't working properly, but only you can determine that by using an oven thermometer.
    – FuzzyChef
    Commented May 11 at 23:07
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    I would expect a refrigerated lasagna to take around twice as long as if it were baked right after assembly with hot filling. But I’ve also had a similar issue as you when doing a ‘no boil’ lasagna in someone else’s oven, and that was freshly assembled (But with cold ingredients, as it had a ricotta layer)
    – Joe
    Commented May 12 at 0:56
  • I have faithfully promised next time I visit I will take both my contact and non-contact thermometers with me. That will, hopefully, resolve this finally.
    – Greybeard
    Commented May 12 at 14:32
  • @Joe that is my partners theory, but it doesn't account for the fact that you can cook a frozen lasagne in less time at a lower temperature. It may well be a combination of factors - lasange size, lasagne temperature and oven efficency.
    – Greybeard
    Commented May 12 at 14:43
  • In my experience, the frozen lazagnes I've had were thinner than what I'd prepare from scratch. That's probably the factor most affecting cook time.
    – Esther
    Commented May 13 at 15:08

1 Answer 1

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I suspect that the oven was only being heated from a top element, either because it was malfunctioning or because you selected the wrong icon on an unfamiliar dial. That would explain the severely retarded cooking and the not-very-hot drip tray.

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  • I checked that it was in fan mode twice. Helpfully, it had a fan symbol on the display that was illuminated.
    – Greybeard
    Commented May 12 at 14:29
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    @Greybeard Fan with only top element active possibly?
    – vidarlo
    Commented May 12 at 16:04
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    While it's possible that only the top element was working, this doesn't seem like a reasonable explanation on its own, given the description of the observed behavior in the question. Even with only a single element working, everything in the oven, other than the mass of the lasagna, should have reached an equilibrium temperature dramatically above the hand-touchable temperature reported. IMO, the only conclusion which can be drawn from the question's description is that something was wrong. To determine what was actually wrong requires more information from the OP and/or more investigation.
    – Makyen
    Commented May 12 at 17:23
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    @Makyen the thermostat for an oven is generally located near the top of the chamber. With only the top element active, even with the fan, there is a huge temperature gradient between the top and bottom. It simply does not make sense to talk about “the equilibrium temperature”.
    – Sneftel
    Commented May 12 at 20:01
  • @vidarlo Quite possible.
    – Greybeard
    Commented May 13 at 16:03

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