Why Freeze-Dry Hash and Cannabis Extractions?

When it comes to hashish and cannabis extractions, the term "freeze dryer" frequently comes up. Increasingly, hash producers are incorporating this tool into their processes.

What exactly is freeze-drying, and how does it work? 

The earliest instances of food freeze-drying date back to the pre-Columbian Inca civilisation, which thrived between the 12th and 16th centuries AD on the Andean plateau. High-altitude freezing preserved food, allowing residual water to evaporate due to the low pressure found at these heights. The invention of the freeze dryer is credited to the French biophysicist and physiologist Arsène d'Arsonval; however, the first modern freeze dryer utilising the sublimation technique, similar to those used today, was built by Léon Shackell in 1909.

In the cannabis industry, freeze dryers are mainly used to dry extractions such as waterhash and, to a lesser extent, sieve extractions. Recently, many growers have also started using them to dry and cure cannabis buds. Utilising a freeze dryer results in very fast drying times while preserving the organoleptic qualities, aesthetic appearance, and cannabinoid content of the processed products. The freeze-drying process consists of three phases:

Rapid Freezing: The material is placed in the freeze-dryer chamber and quickly frozen to -40°C.

Sublimation: Ice is converted directly from a solid to a gaseous state, aided by the vacuum pressure within the chamber.

Desorption (Secondary Drying): This step eliminates residual water molecules by slightly increasing the temperature inside the chamber and reducing the pressure to facilitate evaporation. Rapidly freezing the water results in the formation of very small ice crystals, which helps to preserve the material's structure. Additionally, at such low temperatures, enzymatic activity that can degrade the material is halted, maintaining its integrity.

The sublimation process effectively removes water with minimal terpene loss due to the low temperatures and vacuum conditions. This secondary drying phase reduces residual moisture content from around 10% to 1%. Among various drying methods, freeze drying is the most effective for preserving the organoleptic characteristics and cannabinoid content of the final product.

Traditional drying methods, such as using a drying chamber, often cause significant terpene evaporation and alteration of the cannabinoid profile. Terpenes are highly volatile at room temperature, and exposure to light and oxygen can lead to oxidation, which affects both cannabis buds and extracts by altering their cannabinoid content, shape, and appearance. In its natural state, THC exists as a carboxylic acid (THC-A).

During degradation, THC-A can transform into cannabinol (CBN), a cannabinoid associated with sedative effects. Microbial contamination and risks of fungal diseases, like botrytis—which can rot and ruin the final product—also contribute to cannabis degradation. The use of a freeze dryer effectively mitigates these issues.

As stated, freeze-dryers are primarily used for drying waterhash. They are particularly advantageous for fresh resin extractions, such as Whole Plant Fresh Frozen (WPFF), which can be challenging to handle due to the resin's consistency, akin to quick-setting glue.

The freeze dryer resolves this issue by transferring the still-water-saturated resin from waterhash bags directly into trays within the machine. Once processed, the resulting resin is flawless.

More From Soft Secrets:

What's the story of Moroccan Hash?

10 Top Tips for Making Water Hash