Types of Cannabis Extracts: From Bubble Hash and Rosin to BHO, RSO and CO2

Types of cannabis extracts and how they're made

Cannabis extracts fall into two big families: solventless (mechanical) methods like ice water hash, dry sift and rosin, and solvent-based (chemical) methods like BHO, RSO, tinctures and CO2. Their popularity has exploded in recent years because they concentrate the plant's cannabinoids into a resin. 

An extract made from dried weed is basically the result of concentrating the plant's cannabinoids while throwing out as much plant material as possible. 

What separates one extract from another is the technique. Mechanical methods physically separate the cannabinoids from the plant matter, while chemical methods use different solvents to pull them out. For anyone starting out, the solventless side is the safe place to play; the solvent side is where the real risks live.

Solventless extracts

None of the methods below use a solvent. All you need is water, heat, a few screens and pressure.

Ice-O-Lator hash / bubble hash / water hash:

these three names describe the same extraction process, and they all need the same gear: a 5 to 10 liter (roughly 1.3 to 2.6 gallon) bucket, depending on how much plant material you're working with, and an "Ice-O-Lator" type kit with mesh bags in several sizes, nested from the finest screen to the coarsest.

Let's be honest: it's a seriously simple method. Here's the step by step:

1- Fill the bucket about 2/3 full with cold water, add ice and drop in the bags/filter with the buds inside.

2- The cold water and ice make the trichomes snap off easily. To give the process a little push, you can put the flowers in the freezer for an hour before you start. 

3- To knock the trichomes loose, stir the bag around in the bucket for about 20-25 minutes. Then pull the bag out, drain the water slowly and collect the resin from each bag/screen.

4- The last step is to press the product together by hand and let it dry for at least a week. Set it on a plate in a room that stays at 20-22 °C (68-72 °F) with humidity between 55% and 60%. 

Dry sift hash:

This is probably the simplest and cheapest extraction method out there, so pretty much anyone can pull it off. 

All you need is an extraction bag, the same kind used for the Ice-O-Lator method, with whatever micron size you prefer (keep in mind this directly affects the quality of the final product). The smaller the mesh opening, the smaller the resin glands you collect (we're talking roughly a 50-micron screen). And if you're feeling motivated and up for a bit more work, you can make different grades by sifting through screens of different sizes.

For example, you can do a first pass with a 150-micron bag and then work your way down. A 70-micron bag gets you an excellent dry sift that will seriously surprise you. To sift:

1- Put the herb in the extraction bag and shake it vertically, lightly and very gently, over a smooth, clean, dry surface. The resin trichomes will fall onto it and pile up as a yellowish to whitish powder.

2- Once you've collected all the powder, shape and press it into a compact, uniform piece of hash. The easiest tool is a stiff card, like a credit card. Keep in mind you need dry weed for this; you can also stick it in the freezer for at least an hour beforehand so the cold helps the trichomes come loose. 

It's a dry method, so the extract doesn't need any drying time afterward, and there's no box-drying of buds involved either. It's ready to use right away.

Rosin (rosin tech):

For this one you need parchment paper and a heat press. The easiest, cheapest route is a hair straightener, the kind people use to flatten their hair, as long as it has a built-in temperature control.

Place the bud on the parchment paper, fold it over into a small, tight rectangular packet and squeeze it between the straightener's plates. The heat and pressure turn the resin liquid and it sticks to the paper. Then you just scrape the resin off the parchment and your extract is ready to enjoy.

Solvent-based extracts

These methods are the industry standard today because they can produce large volumes of extract. They typically use solvents like butane, propane, CO2 or ethanol to separate the compounds you're after. 

You'll notice these extracts can vary quite a bit, which usually comes down to the solvent used and the purging methods applied after extraction. 

Whenever a solvent is used, it has to be removed through a process called purging, where the leftover chemical solvents evaporate out of the extract. Since solvents affect the look, texture and smell of the final product, you can end up with a wide range of different extracts.

Below are the extraction methods that use chemical solvents (hydrocarbons and others). 

Before we get into them, a serious heads up: handling chemicals and certain equipment comes with very real dangers, including explosions and fires. This section explains how these methods work; it isn't a how-to for your kitchen. 

BHO (butane hash oil):

This method uses butane gas as the chemical solvent. Other hydrocarbons can be used too, like propane, hexane or dimethyl ether (sold as Dexso, the source of the name DHO). There's also a method that combines BHO + DHO, called DBHO.

The extraction process is the same whatever solvent you use, but the properties of the concentrate change depending on the solvent. 

Here's how it works in principle: 

1- The plant material goes into a sealed container.

2- The solvent is injected under pressure and runs through the plant material, pulling out the plant's essential oils, which carry the active compounds that matter: cannabinoids + terpenes + flavonoids.

3- Then the leftover solvent has to be removed, a step that's essential for a clean, safe extract of the highest possible purity. 

That removal happens through evaporation, heating the extract to the lowest temperature at which the solvent will evaporate so the flavor and aroma don't degrade. Butane is heavier than air and extremely flammable, which is exactly why this is a job for closed-loop equipment and trained people. 

Rick Simpson Oil (RSO):

this technique produces a good-quality cannabis oil that's usually used for therapeutic purposes.

The idea is simple: the whole plant is soaked in ethyl or isopropyl alcohol, which pulls out the cannabinoids efficiently. Then the solvent is evaporated off with heat. Alcohol fumes are highly flammable, so this step is a real fire risk: never near an open flame or a spark. Once the solvent is gone, you're left with a thick, blackish oil. 

This extract is usually taken by mouth: a few drops under the tongue, then swallowed. We won't pretend it tastes good, but some patients report the benefits are worth it. It can also be applied to the skin.

Tinctures:

these are liquid concentrates made by extracting with alcohol. The alcohol does a good job of pulling out cannabinoids and terpenes, and no heat source is needed. The best part: they taste a lot better than RSO.

They're taken by mouth, with the drops placed under the tongue and then swallowed. They're used for some conditions where studies point to possible benefits. 

Live resin:

This technique means putting fresh cannabis flowers in the freezer right after you cut them. There's no need to dry the flowers or the rest of the plant material. 

The big advantage is that the terpenes don't have time to break down from air, light and heat, so they keep their full profile. The result is a top-shelf product that has nothing to envy.

Supercritical (CO2) extraction:

Everybody's after this method because of the quality and purity of the final product. It uses carbon dioxide (CO2) turned into a supercritical fluid. 

A supercritical fluid shifts quickly between liquid and gas when it's held at specific temperatures and pressures, and that's what gets such outstanding results. 

The only downside, if you want to call it that, is that the equipment is expensive. It also takes proper training to run, since you're dealing with high-risk hazards (explosion, fire).

Molecular separation:

This method isolates the plant's cannabinoids and terpenes separately at a moderate temperature, which keeps their molecules from breaking down. 

Those are the main techniques. As we've warned over and over, most of them have to be done with extreme care and the right know-how to avoid accidents that can turn out to be fatal. 

For growers who are just getting into the cannabis world, we strongly recommend sticking with the solventless methods. They let you experiment without risking a disaster or ruining your buds for good. 

How to dry freshly cut buds before extracting

Before extracting (except for live resin, which uses fresh frozen material), keep in mind that freshly harvested cannabis holds a lot of excess moisture that has to go. So the question is: how do you dry weed?

Drying is what turns freshly cut buds into the best version of themselves. First, they need to dry in a dark room for about a week. The longer you let them dry, the better.

Dry buds do several important jobs that ultimately improve quality and extend shelf life. That said, a few factors affect how long drying takes:

-The size of the buds

-How the plants were trimmed

-The temperature, humidity and airflow in the drying room

A slow dry goes a long way toward helping cannabis keep a fuller, richer terpene profile. Drying for longer also cuts down the harshness you feel when you smoke, so if you want strong, tasty buds, patience is the move.

For a great end result, plan on a drying time of roughly 7 to 12 days. As the buds lose moisture, they gradually shrink and get lighter.