Cake – Does the thickness of a cake affect the baking time

A 13" cake is large enough to be a major problem -- the center just won't set correctly before the edges overcook.

You generally want to cook large cakes at a lower temperature than you'd cook a smaller cake at; they won't rise as much, but as they're typically used for stacking, a denser cake may be preferred.

There are also two gadgets that you may wish to consider when you're dealing with cakes over 10 inches:

• Baking Strips : They cool the edge of the cake, so that it cooks slower. Wilton sells them, but you can also make your own from an old towel
• Heating Core : They conduct heat to the middle of the cake, so it'll cook faster. Wilton sells them, too, but if it's not too deep of a cake, you may be able to use a flower nail. If you have a heat safe metal cup, that could work as well; I've heard of people using a cocktail shaker. (but it's important to grease it liberally, as you want what's inside to come out cleanly so it can be used to plug the hole).

I can't help with the gas mark, as I don't know the British system.

The following rule of thumb comes from week 6 in a Harvard University physics course called "Science and Cooking". I took it as a MOOC in the website edx (https://www.edx.org/node/8086).

And the rule is: double the thickness, quadruple the time. If it takes a minute to cook the first outer 0.5cm of the cake, it will take four minutes to cook the first whole cm.

So if you double your cake's size, try to start with multiplying the time by four, without raising the temperature. If the change is smaller, then it might take some rough calculations. But that's the general rule.

Here's the video of the specific part of the lesson that regards discusses the matter: https://youtu.be/fqyVZ5Ifmio