A Cookie Sheet is a flat sheet of metal designed for baking, usually cookies (aka biscuits.)It can also be used for baking many other things from wiener wraps to braided breads, oven fries to cinnamon rolls.
Cookie Sheets are usually made of aluminum or steel. Some models are coated with non-stick surfacing. The sides may be completely open, or rimmed.
Good ones should be stiff, and not flexible.
If you are going to need one Cookie Sheet, then you probably need two. If you’re a real cookie baker, you may want three for times of big production: 1 in the oven, 1 cooling off, and 1 cooled off one being refilled.
Some people feel that the open-sided ones are easier to get the cookies off from, with no rim to have to lift hot, soft cookies over, though even the open-sided ones though usually have one of the sides turned up, to give you a bit of a handle to make it easier to lift it with. Some people even say that the low rims “interfere with heat circulation”, but most home bakers guffaw at the idea.
Insulated Cookie Sheets have an air layer created by putting a bottom sheet under their baking surface, and enclosing that area underneath, trapping air in it. Consequently, they behave differently. The design allows air to circulate underneath, reducing hot spots, which help things bake more evenly. This helps prevent burnt bottoms, and helps ensure that the bottoms of cookies will be the same colours as the tops. Some even say that the tops of cookies will burn long before the bottoms even start to brown.
Cooking time can be longer on these insulated sheets, which gives cookies a bit more time to spread out before the heat solidifies them.
Cookies might not get as crisp on these insulated sheets.
Don’t soak insulated Cookie Sheets in the sink, or water may be trapped in the air layer. If these sheets do get wet inside, just give them some time in a warm oven, maybe along with something you are baking anyway in the oven, or, stand them up somewhere to dry to allow drainage.
Cookie recipes will specify whether or not you should first grease a Cookie Sheet for a particular type of cookie. The less fat in a cookie, the more likely the need to grease the pan.
Cookies tend to be flatter and spread out more on greased cookie sheets. Don’t over grease the sheets, or the cookie dough may spread out too much during baking.
Shortening or oil make a better grease than does butter — save your butter foil wrappers for greasing bread tins with.
Sometimes, instead of greasing, you can use parchment paper to line cookie sheets with. Many people in North America used waxed paper instead, even though the pros say use parchment paper, just because parchment paper can be more expensive in North America.
You can get reusable non-stick liners made of silicone.
Some people advise to only have one tray of cookies baking in the oven at one time. With only one in at a time, the reasoning is, there is better air circulation, and that solitary sheet doesn’t have to go on the bottom rack near the oven’s heat source, where the bottoms of cookies are more likely to burn.
This thinking, though, may be a relic of a relatively brief period in history when an affluent class of consumers didn’t even give fuel costs a second thought. Before that, when you had to chop your own wood to fire an oven, you would have been keeping an eye on your fuel, and even during that time of low fuel costs, working class people were almost certainly always keeping an eye on their “leccy” or gas bills.
To cook two batches of cookies at the same time in an oven, put one sheet on the top rack, and one on the bottom rack. But, put that one on the bottom rack on top of a third, empty Cookie Sheet to give it extra insulation to help stop the cookie bottoms from burning. In fact, such a doubled-up sheet will help prevent bottoms of cookies from burning wherever they are in the oven. Or, simply have an insulated Cookie Sheet, and use it as the one that goes on the bottom rack.
Let a cookie sheet cool before putting more cookie dough on it, or the dough will melt and spread prematurely.