Do your cookie sheets look like mine? Here are my cookie sheets & pizza screens. I use a silpat for making cookies but the pans go naked for roasting veggies. The pizza screens sometimes get sprayed with oil, which tends to leave a sticky residue over time. All were purchased several years ago at a nearby restaurant supply store.
Aluminum gets grody over time. You can scrub and scrub and scrub all you like but they'll never look brand new again.
Unless you know my secret.
Here are the same cookie sheets and pizza screens later that same day. And I didn't even touch them to get them this way. No chemicals, no scrubbing, no water. Nothing! I didn't have to do a dang thing to them after they got all spiffed up, either.
Are you dying to know how I did it yet?
I put them in the oven during its self-cleaning cycle and walked away for 2 hours.
Now, before you go throwing your bakeware into the oven, make sure it's 100% aluminum and can withstand the high heat of a self-cleaning cycle. Don't try this on anything with non-stick coatings, handles, enamel, or heirloom items.
Other than that, bake your grime away. It's awesome. Now, if only my bathroom were this easy to clean.