how to make dry ice

Method 1 of 2: Making Dry Ice with Compressed CO₂

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   Grab a CO₂ fire extinguisher and a pillowcase. You only need three things to make dry ice at home: a CO₂ fire extinguisher, a fabric pillowcase that you don't mind getting dirty, and a wide open outdoor area where children or pets are unlikely to surprise you.

   • You specifically need a CO₂ fire extinguisher for this method, not an ordinary home extinguisher. Most home extinguishers use fine powders of a chemical like sodium bicarbonate or potassium bicarbonate, which won't supply the CO₂ needed to produce dry ice.^[1]
   • CO₂ fire extinguishers are usually used for laboratories, kitchens, and around mechanical equipment.^[2] They usually have a black plastic horn on the nozzle and have no pressure gauge.
   • You can find CO₂ extinguishers at some hardware stores and online specialty retailers.^[3]
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   Protect your hands, eyes, and limbs. Dry ice is so cold that it can easily cause frostbite or "burns" if it comes into contact with bare skin.^[4] Though using a fire extinguisher doesn't require a Hazmat suit, you'll want to take precaution to protect your body from any dry ice that may conceivably drop or get sprayed onto you. Put on the following before you start:

   • Thick, sturdy work gloves (you may wear tight gloves underneath for extra protection)
   • Lab goggles or protective eyewear
   • Long sleeves and pants
   • Close-toed shoes
   • Long-sleeved jacket or lab coat (optional)
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   Wrap the pillowcase tightly around the hose. Put the horn of the extinguisher's nozzle inside the pillowcase. Gather the pillowcase material and wrap it tight around the hose behind the horn. You don't want any gas to be able to escape except through the tight fabric of the pillowcase.

   • Use duct tape to make a tight seal if you're worried about the pillowcase flying off. The amount of pressure in the extinguisher shouldn't make it hard to hold on, but extra precaution never hurts.
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   Give the extinguisher a blast. When you're ready, squeeze the handle and watch the gas shoot into the pillowcase. Keep this up for 2-3 seconds. You may not think you see ice being produced, but it should quickly start to gather up at the bottom. Release the handle after a few seconds. Carbon dioxide vapor will seep out of the pillowcase — this is normal and safe as long as you're in a well-ventilated area as recommended.

   • If you can't get the extinguisher to fire, check for the safety pin, which must be removed to allow you to squeeze the handle.
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   Remove the pillowcase. Carefully take the horn out of the pillowcase. Keep the fabric tight against the horn to wipe off any ice sticking to it. You should find a small pile of dry ice at the bottom of the pillowcase — it will be a crumbly white material resembling styrofoam.

   • Try to keep the bag upright and don't handle the dry ice more than you need to. If you're wearing sturdy safety gloves, you can touch small pieces of the ice for a few seconds at a time, but don't hold on to them for much longer, as they can even hurt fingers through gloves if given enough time.
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   Transfer to a safe storage container. Scrape the dry ice from the pillowcase into a more practical container, like a bowl, a sturdy plastic bag, or a thermos. Keep the dry ice in a single pile and keep the chunks as big as possible to make it last as long as possible. Do not seal the container. If you put an airtight lid on, the pressure of the CO₂ gas will build up, causing the lid to pop off or the container to explode. If you use a lid, do not press it or screw it all the way on.

   • Not all materials are safe for storing dry ice. See below for suggestions:
   • Do not use fine china, ceramic, or glass containers. The intense cold of the dry ice can cause these materials to to contract and break.
   • Do not use nice or fancy metal containers. Dry ice can cause the metal to mar and warp.
   • Do use sturdy plastic containers (especially coolers and ice chests) to store dry ice.
   • Do use thermoses to store dry ice (but do not seal the thermos.)
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   Alternatively, use a CO₂ tank. If you can't get your hands on a CO₂ fire extinguisher, you can replicate this dry ice-making method with a commercial tank of pressurized CO₂, which are sold at welding supply stores and online. The process is virtually the same — simply attach a horn or nozzle to the tank, wrap a pillowcase around it, blast out gas for a few seconds, and collect the dry ice chunks from the bottom of the pillowcase. The required safety precautions for this method are the same as well.

   • Before your purchase your tank, make sure that it has something called a dip tube, which is also sold separately. These tanks will draw liquid carbon dioxide from the bottom of the tank, which is what you want for making dry ice. On the other hand, tanks without a dip tube will draw gas carbon dioxide from the top of the tank, which won't make dry ice.^[5] Often, dip tube-equipped tanks are marked with two white stripes, while tanks without dip tubes have a black finish.^[6]
   • If you plan on making dry ice often, you may want to invest in a dry ice maker attachment, which is essentially a horn nozzle with a fabric bag over the end that can be fastened and removed.^[7]
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Method 2 of 2: Using Homemade Dry Ice

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   Combine with water to make fog-like gas. One of the most common uses of dry ice is to create artificial smoke or fog. This is as simple as mixing dry ice and water — splashing a bit of water onto the ice creates a hissing noise and produces lots of carbon dioxide gas. This is handy for dances, rock concerts, haunted houses, and other places where you might want to create an eerie, mysterious atmosphere.

   • As always, make sure that you make carbon dioxide gas only outdoors and in well-ventilated areas. Though unlikely, producing lots of carbon dioxide gas in an area with poor ventilation can eventually force the oxygen out, making it impossible to breathe.
   • If you use a container with a small vent hole, you can produce a geyser-like contraption where fog shoots out in a narrow jet. This can even be powerful enough to power a small motor or turn a pinwheel.
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   Use dry ice to carbonate liquids. Another frequent use of carbon dioxide is to make carbonated beverages (fizzy drinks like soda, beer, champagne, sparkling water, and so on.) Putting dry ice in water causes it to release carbon dioxide into the water which eventually gathers in the small bubbles that are the mark of any carbonated drink. Though most commercial and home-brew beverage-making operations actually use CO₂ gas (rather than solid CO₂ in the form of dry ice, the latter will still have something of an effect.^[8]

   • Do not drink your beverage while there is dry ice in it. Wait for the dry ice to bubble away completely before drinking. Swallowing dry ice can cause major internal damage — internal tissues are more vulnerable to frostbite than skin.
   • Some people don't like the taste of dry ice-carbonated beverages. You may want to sample the process with a small amount of your liquid before trying it with the main batch.
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   Use dry ice to keep food and beverages frozen. Dry ice is much, much colder than regular ice, so it can obviously keep food and drinks much, much colder. However, the danger with dry ice is that the food or drink may become too cold — put a bottle of champagne on top of dry ice, for instance, and it may shatter or partially freeze, so only use dry ice for foods that are best served frozen (like ice cream, popsicles, etc.)

   • To use dry ice in an ice chest, add your cold foods to the ice chest first, then place the dry ice on top and loosely shut the lid (as always, take care not to seal it completely.) Cold air sinks, so this arrangement keeps the chest frozen most efficiently. If there is any leftover space, fill it with wadded-up newspaper (extra air will make dry ice sublimate (turn into gas) faster.
   • Dry ice also works well for keeping normal ice frozen in a cooler.
   • Typically, you will want about 10 to 20 pounds of dry ice for every 24-hour period you need to keep your food items frozen (depending upon the size of the ice chest.)
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   Use dry ice to store loose food. Surprisingly, dry ice can be used to keep foods like grains, beans, lentils, and pastas fresh. To do this, first place the dry ice at the bottom of a cooler. Make sure there isn't any frost on the dry ice, as this can introduce moisture and get your food wet. Pour your food products over the dry ice. Let this sit with the lid loosely on (but not sealed) for about five to six hours — the ice needs to completely sublimate (turn into gas) until there is no solid left. When this is done, seal the lid.

   • As the ice sublimates, it forms CO₂ gas, which is heavier than air. As more gas forms, it forces the air out of the container. Without any air in the container, it is very difficult for bacteria or pests to survive, which greatly extends the food's life.
   • For this method, you will want to use about 1/4 pounds of dry ice per five-gallon container.^[9]
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   Use dry ice to shrink solid materials. As mentioned above, dry ice is so cold that it will actually cause materials like metal and ceramic to shrink slightly when it touches them. In certain situations, this property can actually be used to your advantage. See below for two examples:^[10]

   • Fixing car dents: If you have a small "ding" on your car's exterior that looks like the metal has been pushed inward, dry ice may be able to help. Use heavy gloves to press a block or sheet of dried ice against the dent. If you can, press it against the inside of the dent as well. Hold the ice in place until frost forms a few inches around the dent, then remove the ice and let the material warm again. Repeat as needed.
   • Removing floor tiles: This trick is great for removing one or two ceramic tiles from your floor. Place a flat sheet of dry ice centered on the floor tile so that it touches its entire surface. Wait until the entire tile is frosted over. If the tile does not pop out by itself, use a few taps from a hammer and screwdriver to loosen the adhesive along the edges.
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   Use dry ice to kill yard pests. Because carbon dioxide is heavier than air, it will displace air out of any container (we saw this in the food-preserving method above.) It's possible to use this principle to kill moles, gophers, and other pests that are tearing up your yard. To do this, push 1-2 inch sized pieces of dry ice into each hole and cover the top of the hole with dirt. Do this for as many holes as possible — ideally, all of them. The dry ice will sublimate and form CO₂ gas, forcing out the oxygen and suffocating the pests.