How dry ice is made.
Dry ice is solid carbon dioxide — and turning a gas into a −109 °F solid is a clever three-step trick of pressure and rapid expansion. Here is how CO2 becomes the blocks, slices and pellets that keep freight frozen, plus the forms it comes in and why.
Dry ice, in brief
Dry ice is frozen carbon dioxide — the solid form of the same CO2 gas that is all around us. It gets its name because, unlike ordinary water ice, it never melts into a puddle: at normal atmospheric pressure it goes straight from solid to gas, a process called sublimation. That is why it is prized for keeping things cold cleanly, with no meltwater left behind.
At about −109 °F it is dramatically colder than water ice, which is what lets it hold food, pharmaceuticals and freight frozen solid rather than merely cool. But CO2 is a gas at room temperature — so how do you get a gas to become a solid that cold? The answer is a manufacturing process built entirely around pressure and rapid expansion.
An overview of dry ice production
Making dry ice means taking carbon dioxide through three states of matter in a controlled sequence. It begins as a purified gas, is compressed and cooled into a pressurized liquid, is then expanded so violently that it flash-freezes into a fine solid snow, and is finally pressed into the dense blocks and pellets you can hold. Each step exists to move CO2 one stage closer to a usable, ultra-cold solid.
What makes the whole thing work is a simple bit of physics: when a compressed gas or liquid is suddenly allowed to expand, it cools sharply. Dry ice manufacturing harnesses that effect on purpose and at scale. The three steps below walk through exactly how it happens.
From CO2 gas to solid dry ice
Three steps turn ordinary carbon dioxide into a −109 °F solid: purify and liquefy it, expand it into snow, then compress the snow into blocks and pellets.
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Purify and liquefy the carbon dioxide
Production starts with carbon dioxide gas — often captured as a by-product of industrial processes such as ethanol, ammonia or natural-gas refining, which keeps CO2 that would otherwise be released to good use. The gas is cleaned to a high purity, then compressed and cooled until it becomes liquid CO2, stored under pressure. Clean, food-grade purity here is what makes the dry ice safe to use around food.
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Expand it into CO2 snow
The pressurized liquid CO2 is released into a chamber at normal atmospheric pressure. As the pressure drops, part of the liquid flashes instantly to gas, and that rapid expansion pulls heat out of what remains — cooling it so sharply that it freezes into a fine, fluffy solid known as CO2 snow, at about −109 °F. This flash cooling is the heart of how dry ice is made.
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Compress the snow into solid dry ice
The loose CO2 snow is then compressed under high pressure in a hydraulic press or extruder. Packed together, it forms dense, solid dry ice — pressed into large blocks, sliced, or extruded through dies into pellets and rice. The form is chosen for how the dry ice will be used, and the finished product is stored in insulated containers because it begins subliming the moment it is made.
Blocks, slices and pellets
The final press decides the form — and the form decides how fast the dry ice sublimates and what it is good for. The rule of thumb: more surface area means faster cooling but shorter life.
Blocks
Large, dense slabs — typically around 10 lbs. Blocks have the least surface area relative to their mass, so they sublimate slowly and last the longest. They are the choice for extended storage, long-distance shipping, and any situation where the dry ice needs to stay solid for days.
Slices
Blocks cut into thinner slabs. Slices balance longevity with a bit more cooling surface, which makes them convenient for medium-term storage and for shipping applications where a full block is more than needed but pellets would sublimate too fast.
Pellets & rice
Small extruded pieces, from pea-sized pellets down to fine rice. With the most surface area per pound, they cool the fastest — used for flash-freezing, blast chilling, dry-ice blasting (industrial cleaning), and the dense fog effects at events. They sublimate quickest, so they are made for immediate use.
The bottom line
Dry ice is a small feat of physics made routine. Purified carbon dioxide is liquefied under pressure, flash-frozen into snow by rapid expansion, and pressed into solid blocks, slices or pellets — a clean, water-free, ultra-cold solid that begins returning to gas the moment it is made. Understanding that it is always subliming is the key to using it well: buy it fresh, match the form to the job, and size the quantity to how long it must last.
That last part — sizing and delivering it so it is still working when it arrives — is exactly what a freight brokerage that moves cold loads every day brings to it. RS Group supplies fresh dry ice in Atlanta, ships it nationwide up to 50,000 lbs, and handles the packaging and compliance when it travels.
Questions about dry ice
The questions people ask us most about what dry ice is and how it is made.
What is dry ice made of?
Dry ice is made of nothing but carbon dioxide — CO2, the same gas that is in the air and that we exhale — in solid form. There are no additives. What makes it "dry" is that, unlike water ice, it never becomes a liquid at normal pressure: it goes straight from solid to gas, a process called sublimation.
The CO2 used is purified to a high, often food-grade standard, which is why dry ice can be used safely around food and drink.
Why is dry ice so cold?
Solid carbon dioxide sits at about −109 °F (−78.5 °C) at normal atmospheric pressure — far colder than water ice at 32 °F. That extreme cold is a property of CO2 itself: it is the temperature at which carbon dioxide exists as a solid rather than a gas.
The cold is created during manufacturing by rapid expansion — releasing pressurized liquid CO2 so that flashing part of it to gas pulls heat out of the rest, freezing it into snow. That flash-cooling step is the second stage of the process above.
Is making dry ice environmentally harmful?
The carbon dioxide used to make dry ice is very often captured as a by-product of existing industrial processes — it is CO2 that already exists and would otherwise be vented. Turning it into dry ice puts it to a second use before it eventually returns to the atmosphere as the dry ice sublimates. In that sense manufacturing does not create new CO2 so much as borrow it.
That is one reason dry ice is a practical, widely used cooling medium — though, as with any refrigerant, using the right amount and not wasting it is the responsible approach.
Can you make dry ice at home?
In principle, small amounts can be made by rapidly releasing CO2 from a pressurized source into a fabric collector, but it is fiddly, wasteful and carries real risks — cold burns and CO2 build-up chief among them. For any practical quantity, buying commercially made dry ice is far cheaper, safer and more reliable.
RS Group supplies fresh dry ice in Atlanta and ships it nationwide, in the form and quantity your application needs.
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