The tin decides the crust as much as the oven does

An oven sets a temperature and a tin sets a rate

Two cakes from the same bowl, baked side by side at the same setting, can come out with visibly different crusts and different heights. Nothing about the oven explains it. The dial controls the temperature of the air and the walls, and that is only the supply; what reaches the batter depends entirely on what stands between them, and for most of the surface area of a cake that is a sheet of metal, glass or ceramic with its own habits.

Three mechanisms carry heat into a tin at once. Air moves past it and gives up heat by convection, the oven walls and elements throw infrared at it, and the tin itself then conducts that energy through to whatever is touching it. A tin isn’t a passive container in any of those exchanges. It decides how much radiation it accepts, how quickly it passes energy on, and how much it stores before it does.

Colour changes how much radiation the tin accepts

A dark, matt surface absorbs radiant heat efficiently and a bright, reflective one throws a good part of it back into the oven. This is why a dark tin produces a browner, thicker crust and a shiny aluminium one gives a pale, soft edge, from an identical batter at an identical setting. The effect is real and it is large enough to matter, particularly at the sides and base where the batter is in direct contact.

Which surface you want depends on what you are baking rather than on which is better. A rich fruit cake sitting in the oven for hours is easier to manage in a pale tin, since the outside has all that time to darken anyway. A pizza-style base or a pastry case wants the opposite, because a fast, hot floor is exactly the point. Most non-stick coatings happen to be dark, which means choosing a non-stick tin also quietly chooses a faster, browner bake.

Glass and ceramic start slowly and then refuse to stop

Glass conducts heat poorly compared with metal, so it warms up sluggishly, but it is fairly transparent to infrared, which lets radiant energy pass straight through and heat the food directly. It also holds a lot of energy once warm and gives it up slowly. The combined result is a bake that lags at first and then browns hard at the base and keeps cooking well after it leaves the oven, which is the source of the conventional advice to drop the temperature by ten or fifteen degrees for a glass dish.

Stoneware and ceramic behave similarly and more so. High heat capacity is precisely what you want for something served in its dish, and precisely what you don’t want for a delicate sponge that needs to stop cooking when you say so. Carryover in a heavy dish is not a rounding error; a custard or a bread pudding will go on setting for several minutes after it comes out, and the moment to pull it is earlier than instinct suggests.

Thickness is thermal mass, and thermal mass is evenness

A thin tin responds almost instantly to the oven around it, which sounds like an advantage and is often the reverse. It also responds instantly to the cold spot when the door opens, and to the burst of radiant heat when an element cycles on, so the batter experiences every fluctuation the oven has. Heavy gauge metal averages those swings out. It takes longer to come up to temperature and it then holds a far steadier one.

Thin tins also buckle. A sheet that warps under heat lifts away from the oven shelf in places and stays in contact elsewhere, which turns a uniform base into a patchwork, and it is the usual explanation for biscuits that brown in a crescent rather than a circle. Heavier tins stay flat. They cost more and they last, which is one of the few equipment arguments in baking where the expensive answer is straightforwardly correct.

What sits between the tin and the batter

Everything above assumes contact, and most of the time there is a layer in the way. Butter and flour make a thin barrier that browns on its own. Parchment adds an insulating gap and slows the base slightly. Silicone moulds are insulators outright, which is why cakes baked in them come out pale-sided and often need longer, and why they are better suited to frozen and set preparations than to anything that wants a crust.

The practical rule is to change one thing at a time and expect the tin to be one of the variables rather than a constant. If a trusted recipe comes out browner than usual in a new tin, the recipe has not changed. Reduce the temperature slightly, move the shelf away from the element doing most of the radiating, or accept the darker crust as a property of the tin, which is entirely reasonable if it is a crust you like.