I never remember what worked before, or to write it down someplace. In any case the size and starting temperature will vary. The instructions I learned from refuse to give a time at all, and the first time my guests were waiting hours past the expected dinner time; another time it was ready so early that I had to call everyone to come right away.
For dinner every Jan 1 I make a rib roast:
which I cook very slowly, as taught by “Good Eats”. I no longer use the flower pot, though, as the oven is good enough to use a open roasting pan.
To summarize, this is the slow method of putting in an oven (or bury a crock in the coals) at (a mere) 200°F
The main variable for me would be the starting temperature. From the ’fridge, it might be a chilly 40° in the center, or might be 52, or anything really depending on how it was aged and when it was taken out. The size is 10 pounds, which is 4 bones. The cross section is the same as the generic picture, but mine is about twice as tall (tall in the photo; but that's width in the oven, if it matters).
So we start out with a thermal gradient, and end that step with a thermal gradient too, as the heat still moves toward the center even after it's removed from the oven. I expect about 10 degrees of “carry over”, which should tell you something about the thermal properties of the material.
Can someone help me with a quick thermodynamic formula that will tell me the expected time until the external heat should be removed, based on the starting temperature of the center? Then, what should I be expecting for equilibrium if the outside is insulated, and how long would that take?
(actually I don't really need to to reach equilibrium because I return to a very hot oven to char the outside; but that's fast enough that the center doesn't know what's happening and intermediate locations are still working on the wave of temp. difference from the original 200° bake).
Best Answer
Typically meat at the usual oven temperature of 350 F takes about 20 minutes per pound. The objective is to get the interior of the roast cooked which means getting it up to between 160 F and 170 F.
In Short, you are using an convection oven at 350 degrees to raise the temperature of the meat from around 70 F to 170 F, a rise of 100 F in N minutes.
If the oven is only at 200 F, does it make sense that it will take a lot longer to raise the temperature of the meat to 160 F to 170 F.
350 - 70 = 280 200 - 70 = 130
280 / 100 = 2.8 130 / 100 = 1.3
2.8/1.3 = 2.154 Times as long. so 43 minutes per pound.
I would use less than this number though, as it is impossible to fix when it is overcooked.