How is dry ice made?

What makes dry ice different

The defining fact about dry ice is what it isn’t: it isn’t frozen water. It’s frozen carbon dioxide — the same CO₂ that’s in the air you breathe and the fizz in a soda. That single difference changes everything. Water freezes at 0 °C and melts back into a liquid. Solid CO₂ sits at −78.5 °C (−109.3 °F) and, at normal atmospheric pressure, never becomes a liquid at all — it sublimates, turning straight from solid to gas. Colder, and with no meltwater, it’s a fundamentally better tool for keeping things deeply frozen.

An introduction to dry ice

Dry ice has been manufactured commercially for about a century, and the basic chemistry hasn’t changed: take carbon dioxide, purify it, and use pressure and temperature to turn it into a solid. The CO₂ itself is usually captured as a by-product of industrial processes — refining, fermentation, and chemical manufacturing all release it — so making dry ice is also a way of reusing carbon that would otherwise be vented. Once it’s purified to the right grade, the rest is a matter of physics applied with the right equipment.

An overview of the production process

At a high level, dry ice is made in three moves: purify the carbon dioxide, compress it into a cold liquid, and then release that liquid so it rapidly expands — which flash-freezes part of it into a fine solid called CO₂ snow. That snow is then mechanically pressed into the dense forms you actually use: blocks, slices, and pellets. Each step matters, so it’s worth walking through them.

The detailed process

1. Purified carbon dioxide

Raw CO₂ captured from industrial sources contains impurities, so the first step is purification — filtering and treating the gas to remove contaminants until it’s clean enough for food and beverage applications. This is what makes the finished dry ice safe to use around food. Quality starts here: clean CO₂ in means clean dry ice out.

2. Pressurization and liquefaction

The purified gas is then compressed and cooled under high pressure until it turns into liquid CO₂. Carbon dioxide only exists as a liquid under pressure, so it’s held in pressurized tanks at this stage. This compressed, chilled liquid is the raw material for the final transformation.

3. Rapid expansion into CO₂ snow

Here’s the moment the magic happens. The liquid CO₂ is released from pressure, and as it rapidly expands it cools dramatically — so dramatically that a portion of it flash-freezes into a fine, powdery solid known as CO₂ snow. (The rest flashes off as gas.) This is the same physics that frosts a pressurized valve when you open it, taken to an extreme. The snow is solid dry ice — just not yet in a usable shape.

Different forms and manufacturing

The loose CO₂ snow is then compressed under mechanical pressure into dense, solid forms, and the shape it’s pressed into determines how it’s used:

• Blocks — large, dense slabs pressed in a block press; the slowest to sublimate, ideal for long transit and bulk cooling.
• Slices and slabs — thinner cuts that layer easily into coolers and shipping boxes around perishable product.
• Pellets and nuggets — small rice- to pencil-sized pieces extruded through a die, used for medical and laboratory cooling and for dry ice blasting.

The denser and larger the form, the longer it lasts before it sublimates away — which is why blocks are the choice for extended shipping and pellets for fast-acting, even cooling.

The takeaway

Dry ice is a small triumph of applied physics: ordinary carbon dioxide, purified, pressurized into a liquid, and expanded into snow that’s pressed into a solid colder than anything in your freezer — all without a drop of water involved. That’s what makes it the cold chain’s most reliable tool. RS Group makes the using part easy: we supply dry ice in Atlanta and ship with it in the quantities your operation needs, sized correctly and handled to spec.