# baking time versus number of items in oven

I doubled a recipe for apple cake, and filled two 13x9 pans. Into the 350F wall oven they went. Recipe estimates 50-60 minutes.

60 minutes later, probe comes out pretty damp, and cakes are more than a bit jiggly. Easy enough, bake a little longer.

What's going on here? Do two room temperature cakes depress the initial temperature for a lot longer than one?

p.s. Oven calibration recently checked, so it's not that.

I was baking these cakes one atop the other, with a few inches between, in an electric oven. I did not have convection turned on.

(1) Are you baking them upper/lower or side-by-side?, (2) Is your oven's outside width 24" or 30"?, & (3) Gas or electric?

My guess would be that either you have a 24" oven and you're baking upper/lower or you have a 30" oven and you're baking side-by-side. Either way, I think the ultimate culprit is heat circulation - certainly you wouldn't be having this problem in a convection oven, right?

If you're baking them upper/lower in a small oven, I believe that heat absorption would probably create areas of lower temperature above both pans that wouldn't even out well without convection. If you're baking side-by-side in a larger oven, I believe that the total area of your pans would create a heat block and a temperature differential between the top and bottom of your oven that would not dissipate well without convection. And while I think the circulation problem would be less of a problem with gas, I'm pretty sure it's going to present a problem in either type of oven you use.

Being the owner of a 24" electric oven myself (so the interior of my oven is 18" x 18", not including the ribs that support the racks), I can't even bake two 9" circular cake layers at the same time (either diagonally or upper and lower) without grotesque deformations in the tops of my cakes. And two 9" round pans with a thin layer of cake batter are going to be less of a heat magnet and obstruction than a thick layer of apple cake batter in two 9" x 13" pans.

Ultimately I think the problem is not one of time but of maintaining temperatures above and below your pans - and adding time to the bake won't resolve the problems caused by such a differential. Alas, I believe that your best option is to give each cake its own space and time in the oven. Whether it's a heat conduction issue or a circulation issue or some combination of both, I think the variables involved are WAY too complicated to ever lead to a general baking time extension guideline when doubling-up a recipe.

Bake them separately - and, yes, I realize that's not a very satisfying recommendation.

• Well, I swapped the cakes, turned on the convection feature, and baked another 30 minutes. As far as we've cut into one of them, it's quite satisfactory. Next time I'll convect to begin with or use two ovens. I don't often make this much cake :-) Sep 28, 2014 at 21:44

Yes, two cakes will take longer than one, but only by a tiny bit. The second cake is an additional heat sink, but it shouldn't be enough that you'd notice it if they're on the same shelf. Did you open the oven to switch the places of the two cakes? If not, you should have, and that would definitely increase the cook time. If the two are on different shelves, one would block some heat from the other.

• In an oven with a thermostat and temperature control, does the heat sink effect still matter? Or does the oven compensate for it by increasing the on time to keep the temperature setting? Mar 6, 2015 at 1:34

Do not put one cake on top of other..Always, if you have to put side by side with inches between or one to left and one to right on diffrent racks but never over each other..

You should never cook 2 cakes same oven, same time=problem! Easy fix, cook seperately!

• Sure, that's the easiest fix, but there must be some way to calibrate a workaround. Say you're pressed for time and you simply don't have long enough to bake one cake, then the other - what then? Oct 1, 2014 at 14:44