A coworker of mine made two trays of cookies in the same oven, cooking them at the same temperature for the same time. One batch was thinner than the others, and that batch was also less blackened on the bottom. Why?
Were they both in the oven at the same time? Perhaps the oven in the first batch wasn’t up to temp and they heated bottom first. Were the trays made of the same material? What made the second batch thinner? Did she add something to the second mix?
Nope, same recipe for both, although obviously there was less of it for the thinner ones. Presumably the same tray, and presumably the thinner ones were made second.
The cookie sheet might have been hot when the second batch was placed on it (it is when I make cookies). That’ll heat the dough before it goes into the oven, maybe even melt some of the butter.
continued.
Having partially melted outside the oven, the cookies end up thinner. The second batch usually comes out of the oven in a few minutes quicker than the first batch. That gives them less time to burn.
My WAG is that the turpentine might play a part in this…
No, seriously, I too say it has to do with the temperature of the plate.
I agree. The thinner cookies melted quickly, and cooke faster, so they were done before the bottom burned.
You say there was a lot less dough in the thinner cookies. Assuming this is true, how could the cook know to put in less dough per cookie at the time she was placing the dough, before it went into the oven? Answer, the second batch immediately began to spread out more rapidly (began to melt immediately) and it was visibly obvious that putting the same amount of dough in the same pattern would have resulted in the cookies running together.
Another possibility: most ovens have warm spots & cool spots.
The tray with the thinner cookies could have been placed in a part of the oven that was not as hot as the other tray.