beakers full of liquid

How to Make Shatter with CO2 – Supercritical Extraction

CO2 shatter is a type of cannabis concentrate. It’s becoming more and more popular for some very good reasons…

For a start that’s because – unlike other solvents used in cannabis concentrate extraction (such as butane or propane) – CO2 will leave no potentially harmful contaminants behind.
Plus, as with all properly-made cannabis concentrates, CO2 shatter can contain as much as an 80-90% concentration of the specific compound which you’re trying to extract, such as THC or CBD.
That’s far more than would ever be found in the raw plant material with far fewer of the contaminants.

But make no mistake, for all these advantages, the CO2 extraction process is hard.
It requires special equipment, a certain degree of technical knowledge and plenty of time too…

What is supercritical CO2 extraction?

Supercritical CO2 extraction uses a special machine which both heats and compresses CO2 gas until it reaches a supercritical state.

A supercritical fluid exists at a certain critical point of temperature and pressure where it is not quite a liquid and not quite a gas.

Here’s how it works:

When it is at room temperature CO2 is, of course, a gas. You can also turn it into a solid relatively easily (that’s what dry ice is).

To make CO2 into a liquid – or at least give it some of the useful properties of a liquid – you need to make it very hot and very compressed.

When it reaches a certain point, the CO2 will retain its density like a liquid and fill a container like a gas. It has reached a supercritical state.

Why is supercritical CO2 extraction so useful?

First of all, CO2 is considered particularly safe as it is a natural by-product of how the human body works. It is:

leaves sprouting from a drop of water

  1. Non-toxic.
  2. Not flammable like butane or propane.
  3. So safe that you can find it in any bottle of fizzy drinks (it gives it the fizz).

The extraction process is also harmless for the environment and can be used to extract very specific compounds from the raw cannabis plant (in this case) by changing the pressure the CO2 is at, and thus its solubility.

In fact, supercritical CO2 expansion is already used as a safe, affordable and recyclable industrial solvent in a wide variety of industries:

  • Health and beauty (perfumes, omega-3 oils)
  • Food and drink (coffee, tea, vanilla, fruit and nut extracts)
  • Alcohol (hop oil extraction in the beer-making process)
  • Tobacco (extractions for e-cigarettes)
  • Energy (algae oil extractions – an alternative energy source)

Subcritical CO2 expansion – what’s the difference?

Subcritical CO2 expansion is also used in some industries. This process retains the pressure of the supercritical process but reduces the temperature so that it is below the supercritical threshold.

The result is a non-supercritical liquid. This can still be used in the extraction process, but it will work more slowly and produce smaller final quantities.

However, this slower process can actually be a benefit as it is kinder to the more fragile parts you might want to extract (this could mean essential oils or terpenes when we’re talking about cannabis).

How to make shatter with CO2

Returning solely to cannabis extraction, here’s a quick rundown of how to make shatter with CO2:

1) Load the vessel

There are several brands of extraction machines available. Apeks is perhaps one of the most prevalent, but most work in a similar way.

Part of the machine is known as the extraction vessel. This is loaded with the raw, dried plant material and sealed.

cannabis extract

2) Extraction

Then the machine pumps the heated and compressed, supercritical-state CO2 into the extraction vessel.

Now that it has some of the properties of a liquid, the CO2 will fill all of the empty space in the vessel and get to work as a solvent.

3) Decompression

Then the liquid-gas will be pumped into a different part of the machine.
To get there, it passes through a smaller segment which decompresses it back to being more gaseous (remember – it was the combination of temperature and pressure which created the supercritical substance. Now that the pressure is changed, we have a gas again).

4) Collection

The majority of the decompressed material will become a thin almost-liquid substance in the collection vessel attached to the machine.
But the decompression process will also spray some of the extract onto the walls of the vessel. This thick, sticky part is what will be used to make shatter.

5) Oven cooking and cooling

Once that material has been removed from the walls of the chamber, it is placed into a vacuum oven set at about 100 ºF or 37 ºC.
Around 15-20 minutes later the material can be taken out and placed on a very slick surface (this is important as it will be easy to break if you can’t remove it from the surface easily) where it will be allowed to spread out and then be folded over several times.

After it has cooled down, a sheet of shatter will have been created.

CO2 oil vs. distillate

As a side note, one optional extra step which can be applied to the CO2 oil creation process is distillation.

In the same way that distillation is used to remove methanol (which is toxic) in the alcohol brewing industry, it can be used to purify cannabis oil.

Cannabis distillate can be as much as a 99% pure extract from the original plant. There will be no impurities from the production process (not that CO2 includes any) or contaminants like chlorophyll from the plant itself.

The exciting additional medical benefits of CO2 extraction

Supercritical CO2 extraction is useful for people who take cannabis or medical marijuana for a wide variety of complaints as it is a process which results in a much purer source of the beneficial compounds found in the cannabis plant.

But, it is even more exciting from a future medical research point of view:
Supercritical CO2 can be used to extract very specific compounds from the raw cannabis plant. THC (tetrahydrocannabinol) and CBD (cannabidiol) are already having research done on them.

Yet, there are numerous other cannabinoids which, though they might be less prevalent in the cannabis plant, may be potentially equally or even more important from a medical point of view.

Especially now that they can be individually extracted and studied alone as well as in combination with each other.

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