How To Pre Soak Fresh or Cured Material Before Washing for Ice Water Extraction


Todde Philips

🇺🇸 Retired veteran, father, rock-climbing expert & rosin connoisseur.

For thousands of years hash producers have been extracting resin-filled trichomes from cannabis flowers, creating a pure and potent concentrate that captures the most desirable qualities of the plant. The first hash was collected directly by hand from mature flowers, creating a smear of resin by rubbing open palms across the plants. The hash was then peeled away and rolled into balls, called Charas. 

As time went on, other variations of hash making came into use, such as sieving dried cannabis flowers over a piece of woven fabric. The trichomes that fell through the fabric were then collected, known today as dry sift. As the name implies, it relies on dried plant material for proper production. But the problem is that sifting dried flowers also releases tiny pieces of the plant material, which break apart due to their brittleness and fall through the sieving screens along with the trichomes. Any plant material that joins the trichomes is considered contamination in hash. The goal is always 100% full, mature trichome heads. 

Why Washing Hash Is Better

Just 50 years or so ago (which is like yesterday along the full timeline of humanity's rich history of hash production) a new way to make hash was discovered, a way that relies on water to separate trichome heads from the rest of the plant. The method is similar to dry sieving in the use of filter screens, but different in how the trichomes are made to fall away from the plant. With ice water extraction, cannabis flowers are stirred together with ice water, and the vortex created in the water gently pulls the trichomes away from the plant. Then, the trichomes are filtered out of the water using a set of filter bags, called bubble wash bags. The resulting hash is called bubble hash, and it’s one of the most coveted cannabis products available. 

A clear advantage of washing hash over dry sifting is that the plant material is soft and supple in the water, rather than dry and brittle. Dry cannabis by nature releases tiny plant fragments that shatter away from the crispy material, and these can easily pass through the filter screen along with the trichomes. Saturated cannabis, however, remains pliable and spongy, and much less prone to pulverizing with the agitation of extraction. 




What Does It Mean to Pre Soak Cannabis?

Pre Soaking cannabis is an essential first step to thoroughly saturate the material for ice water extraction. Whether you’re washing fresh frozen or dried material, pre soaking in ice water is the way to guarantee the cannabis is soft and springy enough to withstand the agitation without splintering tiny plant fragments along with the trichomes. Skipping this pre soaking will result in noticeably greener product, a clear sign that there is plant material in the hash. 


Pre soaking takes place in the vessel you’re using to mix the ice water and cannabis together, and before you begin any agitation. Once pre soaking is complete, you can move on the the next step of the ice water extraction process. Read the full overview of how to wash hash in our guide How To Wash Bubble Hash

The late Frenchy Cannoli, an icon in the world of hash production, employed a method of pre soaking he called the ice sandwich. Let’s take a look at it. 

How To Pre Soak Cannabis

Creating layers of cannabis and ice, like an ice sandwich, helps keep all the cannabis material fully submerged under water, and to soak in the water evenly. 

First, place a layer of ice along the bottom of the vessel. If you’re using a washing machine, this ice has the extra benefit of reducing the likelihood that resin will get caked on the turning plate and jam it. 


On top of this baseline of ice, place your cannabis material in a nice even layer. Then, place a thicker layer of ice on top of the material, which will keep the cannabis weighted down and completely submerged under water. Once the ice and cannabis is loaded in the mixer, pour in clean, cold water (ideally RO). Make sure all the material stays submerged. 

The rate of rehydration is different for different types of material. Fresh frozen, trim leaves, and dry buds will take different amounts of time to fully saturate with water. Plan for up to and hour, but it may take less time than that. 

In general, pre soaking is complete after 30-60 minutes under water. The best way to know it’s complete is to feel the cannabis material. That said, fresh frozen material generally requires much less time to reach the desired supple, spongy state (5 mins or so). 

Gently separate a flower and see if it feels soft and supple on the very inside. Squeeze it between your fingers and make sure it feels totally springy and spongy. If there is any part that still feels brittle, the material isn’t ready. It shouldn’t snap, break, or tear when you apply some force between your fingers. Everything should feel soft and supple. 

After the material has been thoroughly pre soaked, it remains vulnerable to fragmentation only through force against the ice. If you pre soaked your cannabis and you’re still ending up with greenish hash, you likely use too much ice, too much force in agitating, agitate for too long, or wash the same material too many times (or a combination of the above). 





The beauty of using water to sieve cannabis trichomes is that it allows us to work with rehydrated material that’s soft and supple. Unlike dry sieving, which involves working dry and brittle material over a series of mesh screens, rehydrating cannabis for ice water extraction renders the material less likely to shred into tiny pieces and contaminate the bubble hash.  

It’s not enough to allow this rehydration to happen simultaneously with the agitation phase of extraction. The material needs to be pre soaked in ice water to prime it for the process. Allow for 20-30 mins to pre soak before you begin the extraction. This easy preparation goes a long way in enhancing the purity of your final product. 

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What does it mean to pre soak cannabis for washing bubble hash?
Pre soaking means to submerge cannabis under ice water until it’s completely saturated before starting the mixing process of ice water extraction. 

Do you have to pre soak cannabis before washing bubble hash?
Yes, it’s a necessary first step to prevent excess plant contamination from getting into your final product.

What if you don’t pre soak cannabis before washing hash?
If you don’t thoroughly pre soak cannabis, it will remain brittle and prone to splintering off tiny pieces of plant material, which will contaminate your hash. 

How long do you have to pre soak cannabis before washing hash?
Generally 20-30 minutes, but the time can vary.

How do you know when cannabis has pre soaked long enough?
The material should be squishy, spongy, and incredibly supple, and there should be no dry or brittle parts. Break apart some buds and check that the leaves don’t break (sign that they’re still dry) and that there are no dry spots inside.


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