The duct tape of the kitchen
All kinds of useful
Some of the following uses may surprise you. Some may anger you. Others may just leave you thinking, "I knooooow, I totally use it that way every day." Either way, these aluminum foil tips and tricks may just save your life, so settle in, grab a beverage, and position your roll of aluminum foil so you can gaze at it lovingly while I extol its many virtues.
*To those of you who speak British English, the syllabication doesn't quite work here. Aluminum was given an extra i to make it sound like all of the other -ium elements: helium, plutonium, uranium, etc. This is equally correct; I'm just going to use the lazy American disemvowelled version. In the meantime, don't go getting any ideas about platinum. It'd sound weird with an extra i. Say it aloud, "Platinium." That's how aluminium sounds in the colonies. Rich and vibrant and just a little bit vowelly.
Step 1: Use It in the Kitchen
Pie crust protector. Some aluminum foil folded over the crust of a pie will keep the crust from browning and blackening and eventually falling off before the rest of the pie has cooked sufficiently. This use: useful but not unusual. Its usefulness far outweighs its ordinariness.
Pressure cooker lifter. Placing and lifting bowls into and out of a pressure cooker can be dangerous. Hot food, hot bowls, and slippery surfaces make for a situation fraught with danger. Aluminum foil makes an excellent lifting apparatus to safely and securely raise the precious contents of your pressure cooker without scalding your hands, arms, counter, floor, or curious dog. Just use a piece of aluminum foil that's the size of your bowl plus about eight additional inches. You're making a sling of sorts to lift out the bowl with your newly-made aluminum handles. Fold the foil lengthwise two or three times for strength, then place your bowl into the cooker with your shiny improvised lifter. Fold the handles down during cooking, then use them to lift out your hot bit of deliciousness.
DIY cake pans. Oh no! It's your nephew's birthday and you were supposed to get him a cake shaped like Darth Vader wearing bunny ears. But you forgot because you were busy mayonnaising your hair. Don't panic! You can make yourself an awesome custom cake pan using aluminum foil and some creativity. Just use some aluminum foil inside another baking pan to create the outline of whatever cake you're trying to make. (This is great for county fairs when you want to make something in the shape of the county to woo city council into preferring your home-baked tribute to local government.)
Oven cleaner. You can protect your oven from thrills and spills by placing a few sections of aluminum foil beneath something that might bubble, bubble, toil, and trouble all over the floor of your oven. Don't foil the actual floor of the oven, as that could cause a build-up of heat to warp the bottom of your expensive appliance. Instead, lay some foil over the rack just beneath whatever it is that might erupt and create a mess. Instead of scrubbing until your elbows run out of grease, you can just ball up the soiled foil and recycle it. BONUS OVEN TIP: to protect your heating elements from the harsh chemicals in store-bought oven cleaner, put some aluminum foil over them before spraying down the interior of your oven. [EDIT] This may cause a potentially explosive chemical reaction, but your heating elements will appreciate your thoughtfulness while the house burns down.
Scrubber. I'm a big fan of cast iron frying pans. They're great, but clean up is sometimes a disaster. Using salt and paper towels works most of the time, but egg and rice (and the combination thereof after fried rice) tend to grip the pan like limpets. With a little bit of crumpled aluminum foil, I can scrub off tough messes. This works anywhere you might find yourself scrubbing unusually hard like post-casserole Pyrex, forgot-about-the-pasta-and-all-the-water-boiled-off pots, and caramel that's Maillarded to the point of crumbly blackness.
Campsite cooking utensils. The next time you're camping, you can lug around an entire kitchen set, or you can take a light roll of aluminum foil and fashion your own utensils and pans. You can make a frying pan using a forked stick with aluminum foil stretched over the crook. You can easily make plates and bowls, wrap veggies and meat, or even fold a spoon, fork, or spork out of aluminum foil.
Reheat crispy things. I enjoy the occasional pizza delivered to my door from a company whose name comes from a popular dotted-tile game. But I can't always finish the pizza in one sitting, and I need to reheat the delicious cheesiness. I'll microwave when I'm in a rush, but if I want ideal flavor I go to the oven with some aluminum foil. I set the slice directly on the foil and fold an edge over the crust to protect it from the heat. Bake at 350F for five or so minutes (or broil in high for two) and bam!: fresh-ish pizza. This method has the added advantage of instilling false olfactory hope in a roommate.
Step 2: Use It in the Garden
Protect saplings from deer and rodents. During the wintertime, the tender trunk bark of younger plants is a treat for starving animals. If you don't want Bambi to make it to spring, just wrap your trunks in aluminum foil for the winter. It should protect your shrubbery until the rosy-fingered dawn brings warmer and longer days later in the year. Don't leave it on while the plant is growing because it will need some room to grow.
Keep hungry slugs and bugs out. You work hard on your garden only to see the fruits of your labor devoured by God's creatures great and small. To keep the small ones from munching on your plants, make an aluminum foil mulch. Weed your bed, then lay normal weedblock over it. Place aluminum foil, shiny side down, over the weedblock to create a barrier that will send virus-spreading aphids elsewhere. (Reynolds also sells a special aluminum-treated paper for this purpose.) UC Davis suggests that it will work. If there are any green thumbs out there who have tried this, let me know how you did it in the comments. There is evidence to suggest that simply mixing in aluminum foil strips may have a similar effect, but I can't find any information to back it up that isn't on eHow.
Make a sun box. My apartment faces west, so the sad herbs in my balcony garden all reach out towards the setting sun instead of straight up. Rather than just rotate them every couple of days, I use a sun box (aluminum foil in a shoebox corner) to reflect the sun back into my plants. The box sits just behind the plants and is slightly less unsightly than a battery of cilantro aimed outward towards the San Francisco Bay.
Step 3: Use It for Cleaning
Scrubber: Ball up some aluminum foil and use it to scrub off the nasty, stuck-on messes that get left behind on your non-non-stick pots and pans. This is great for those times when you cook, say, a casserole with some foil on top. You can use the same foil for clean up and then recycle it.
Protect soap bottoms: I haven't used bar soap in forever. Not because I'm averse to washing, but because my soap dissolves into a damp, squishy mess before I get the chance to use it all up. But with a little bit of aluminum foil, I might be able to keep my bars of soap alive long enough to actually use them. To protect your bars of Ivory, just put a layer of aluminum foil on the bottom of your soap. It will protect your soap from melting slowly like the Wicked Witch of the West getting waterboarded at Guantanamo. And it looks nice next to a stainless steel basin. Very modern.
Slide furniture/ protect feet and legs: Sliding furniture around on carpet is sometimes a pain. They sell special furniture-sliding disks for this purpose, but I don't want to buy something just to adjust my couch a few feet. Some aluminum foil on the bottom of the legs allows you to slide your davenport around cheaply and easily. You can use a little extra foil and make some furniture leg-warmer-style protectors when you're mopping or staining or setting your Roomba loose.
Foil the fireplace
Step 4: Use It for Laundry
Ironing speed: I learned to iron when I was a kid and had nothing to iron. Now that I have a closet full of Oxfords and other button-downs, I should be ironing. But I hate it. When I can't steal my girlfriend's hair straightener to fix the placket or collar, I use a layer of aluminum foil on the ironing board to speed up the process. The foil reflects the heat back into the shirt (as opposed to heating up the board itself), so the ironing takes just a little bit less of my life from me.
Attaching patches: My favoritest pair of jeans ripped when I was in college. They fit wonderfully and looked great until I started clumsily jumping chain-link fences. Rather than throw them out, I thought I'd put in a nice patch for visual drama in the back pocket area of the pants. My plan was fool-proof: get an iron-on patch, then iron it on. And it worked! Too well. I ironed the patch over the hole, where it stuck very nicely. It also stuck to the inside of the pants, which was less nice. When I tried to release my one-legged pants from their patchy prison, I ripped them beyond redemption. (I know, I should have reheated the patch before yanking on it. Hindsight. You know.) If I had used a small piece of aluminum foil in my pants to protect the insides, I could still be wearing those pants RIGHT NOW. Aluminum foil, where have you been all my life??
Clean your iron: Sure, my iron doesn't get enough use to get dirty, but it might. Someday. To get those unsightly chunks of melted plastic off of the nonstick sole plate (why'd you leave the iron on high on top of your buttons?), just run the iron on high over a piece of aluminum foil with some salt on top. The abrasion of the salt will help get the plastic off. Don't scrub the nonstick coating, though.
Steam silk and wool: Use the same technique as the speed ironing technique above. Put some aluminum foil on the ironing board, then put your wild and wooly sweater on top. Use the steam setting on your iron and hold it a few inches away and ghost-iron your garment. The foil should reflect the heat back into the piece of clothing. Just make sure not to get too close or you will have to try the patching technique you just read about.
*This means that I probably made this up. I swear that I read it somewhere, though. On the internet. Which means there's a good chance someone else made it up. Either way, it seems to work.
Step 5: Use It in the Garage
Polish chrome: Full disclosure- the sweet, sweet hog pictured above does not belong to me. I do, however, have some chrome surfaces in my home. Escutcheons, especially. Because the chrome coating is contractor-grade thin, I've noticed some unsightly rusty pitting. To clean these off and restore their escutcheony luster, a little bit of aluminum foil and water will buff out those spots and make my bathroom look shiny and new. Rub until it looks good.
Bbq drip pan: Does your bbq drip drops of sizzling fat and crusty chicken chunks? Do you not want to scrape and scrub the bottom of your grill every time you get a hankering for some smokey goodness? Put a layer of aluminum foil over the surface that you'd prefer not to clean. That's it. That's the tip. It'll prevent you having to get a special brush or expend any effort at all to clean up after grilling. Which is good, because that time should be reserved for a food coma punctuated with the occasional meaty belch. (This tip also works for fireplaces.)
Clean the grill: You can use the leftover foil to scrub off the grill rack. It's remarkably satisfying when the foil shapes itself to scrape off a few rows of wire at a time. Not quite as effective as a grill brush, but it'll do in a pinch. (Say, when you're barbecuing at a public park and forgot your grilling utensils. Take nothing but pictures, leave nothing but footprints, guys.)
Step 6: Use It With Technology
Photography light reflector: Taking photos for my Instructables is always a chore. I hate that I have to wait for the light to be right at the office or at home, so I could really use one of those big light reflecting thingamajigs* that real photographers use. With some aluminum foil layered over a piece of cardboard, properly-lit pictures are just a light source away.
Fix loose batteries: Sometimes the springs that hold batteries in place loose their springiness. With their springiness compromised, battery-powered devices might not work at all, or only work if you hold them in a certain position. (I'm looking at you, Comcast remote control that I had to hold vertically in order to DVR Real Housewives of Albuquerque.) With a folded up piece of aluminum foil, you can force those batteries back into place. Just fold up a little piece and wedge it into position so that the battery terminals line up correctly. This trick will blow the mind of a child whose Furby is acting up.
Protect your brain waves from eavesdropping and mind control: Your thoughts are private. The government and super-advanced alien races (especially considering that they are probably in cahoots) shouldn't be able to read or control those thoughts. To combat telepathic control techniques that rely upon radio waves, you can fashion a protective helmet out of aluminum foil. Berkeley engineers have tested the wave-blocking power of aluminum foil and discovered that an aluminum foil deflector beanie actually magnifies extraneous signals beamed into a subject's head at certain frequencies. Probably propaganda. (You can see their results here and decide for yourself.)
*Technical term, obviously.