Cookie sheet issue (or, is it my oven?)
I got some new cookie sheets......problem is......everything seems to be browning on the bottom wayyyyyy too quick. I even doubled up the cookie sheets recently to try to solve this dilemma. This happened with new muffin tins, as well. Both are nonstick.
Maybe my oven is not calibrated correctly? How do I test this?
In a pinch I have used Aluminum foil wrapped on the bottom rack to prevent scorching -- which IMO is caused mainly by radiant heat from the bottom element. Make sure to leave some space on the sides so convective heat isn't too constricted.
You can also try a pizza stone or terracotta tile on the bottom rack if you have one.
Plain old bare aluminum cookie sheets, in my experience, perform better than anything else when baking cookies (and other baked goods).
If you're attached to your nonstick, just turn the heat down by about 25 degrees F (10-15 degrees C), and make sure you preheat. If your oven is electric, wait for a heating cycle to end and *then* put your trays in the oven.
Dark metal absorbs the infrared heat being radiated from the walls and elements better than plain aluminum, and transfers that heat to the food *on top of* the conducted heat from the oven air. That means anything in contact with the dark metal is getting 25 to 50% more heat compared to the parts only heated by the oven air. It doesn't even out until the cookies or whatever you're baking start to brown. The oven might be 350 degrees, but the extra heat absorbed by the dark metal means the cookie sheets may be 400 degrees or even a bit more while the elements are in their 'on' phase.
do they have dark, nonstick surfaces? they tend to encourage over-browning. you're much better off with light-colored cookie sheets.
if it's not the sheets, try moving them to a higher rack when baking to put more distance between the bottom of the pan and the heating element...and test the temp with a good thermometer on both the top and bottom racks to see if you have uneven heating issues.
I'm a fan of the extremely cheap, bright-shiny baking pans that are covered with a microthin layer of tin. They're practically nonstick, but the tin plating is so thin that it wears away quickly. I'm terrible about beating up cookie sheets, so the cheap ones allow me to buy new ones every two or three years and not feel the need to take extra-special care of them. I find that the cheapo ones last me the same duration as the expensive, heavier aluminum ones.
Obviously, there's no harm and only good that can come from properly calibrating your oven with a true oven thermometer. You know, the kind that will set you back about $6 at Bed Bath and Beyond... Word to the wise, though... Don't drop it in a sink full of dish water. I hear that's a bad thing... Speaking of which, I should probably go to Bed Bath and Beyond soon...
You can always try moving the cookie sheets to the top, and make sure that you're using parchment paper or a silpat. Another recommendation is that you let your oven heat up for about 30 minutes before you put in the cookies, so that it doesn't have to "catch up" as much when you open and close the door.
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