Based on archaeological records, humans have relied on hash for spiritual and medicinal purposes for millennia. As recently as May 2020, the Journal of the Institute of Archaeology of Tel Aviv University published new evidence of hash use dating back to the Iron Age, from the Judahite Shrine of Arad in Israel.

Hash production has continued using traditional techniques like it has for thousands of years. The hash producing regions of the Himalayas or Morocco very likely make hash in similar ways to that of the 8th-century hash discovered in Israel, which is to say by hand. But, the rise of legal cannabis markets has launched a brand new era of innovation for hash production. One of these elevated techniques is cold water extraction, also sometimes called ice water extraction or cold water extraction.

Freezing temperatures and agitation remove the need for harsh solvents, which have taken over the industry in recent years. Brands are returning to ice water hash to create the clean, pure, and solvent-free concentrate their customers are now looking for. Coldwater extraction also plays into the new trend of terpene forward concentrates, like live resin and High Terpene Full Spectrum Extractions.

What is Cold Water Extraction Hash?

The principle behind cold water extraction is the clean preservation of cannabinoids and terpenes, with no added ingredients. With consumers increasingly leery about petro-chemical-based extraction techniques, it’s unsurprising that many producers are once again working with cold water (or ice) extraction techniques.

Ed Rosenthal, the grandfather of cannabis cultivation and extraction techniques, explained that cold water extracts rely on “water, ice, and agitation.” When subjected to these ingredients, the microscopic trichomes caking the surface of the flower become extremely brittle. During agitation, these trichomes break off into the ice water wash. Trichomes are fat-soluble and therefore are easy to collect with fine mesh bags. Once dry, the loose cannabinoid trichomes are pressed into balls, bricks, or sold as powdered kief-type products.

Coldwater extraction, as the name suggests, is a process that operates in temperatures at or below the freezing point. This protects many more of the most sensitive compounds than is possible under solvent extraction conditions.

Unlike other extraction techniques, cold water extract is simple and affordable enough for small scale producers to adopt. But as the commercial market has begun to shift away from petrochemicals toward more natural production standards, even commercial facilities like CaliHash are working with cold water extraction these days.

As Calihash explains, a cold water extraction “fundamentally respects the integrity of the original cannabinoid profile.” Under most extraction processes, extreme heat and pressure often come into play. These harsh conditions destroy or alter the most volatile cannabinoids and terpenes. In some cases, the extraction goes through such high temperatures that the final product is nearly devoid of a terpene profile.

How Does Cold Water Extraction Compare with Modern Hash-Making Technologies?

Generally speaking, modern hash production for legal markets falls into two categories: solvent-based and non-solvent-based. For the last decade or so, solvent-based hash extractions have come to dominate the market. By now, concentrates like butane honey oil (BHO), wax, shatters, and resins are commonplace at most dispensaries.

Solvent extractions use butane, propane, ethanol, or CO2. Producers mix cannabis flower (or trim) with the chosen solvent to dissolve the valuable cannabinoids and terpene from the plant material. Once dissolved, the mixture is exposed to high heat to evaporate the remaining solvent, leaving behind a highly concentrated product. Solvent-based extractions vary widely in their texture, consistency, and terpene content, depending on several factors.

A well-extracted concentrate will contain no measurable contaminants from the production process. Still, there is a risk of these chemicals ending up in the BHO, wax, or shatter purchased by the end consumer. To reduce the risks, legal markets all require some level of testing for contamination. Each market has a different set of acceptable limits for the most common chemical contaminants, like pesticides, fertilizers, and solvents. 

Nate Seltenrich pointed out in his 2019 article for Environmental Health Perspectives that many of these acceptable limits were pulled from those set for producers of herbal medicines and other drug products. However, these industries do not use butane or propane, the two most common chemicals in cannabis extraction. Without an example to work off of, Saltenrich explains, “state regulators are left to their own devices,” and “this has led to a huge range of residue limits for the solvents among legal states.”

Finally, many solvents may also have acceptable limits for ingestion, according to the Food and Drug Administration. Still, there are no test results for inhalation, as would be the case for cannabis concentrates. It remains to be seen whether there are risks associated with long-term exposure to solvent-produced cannabis concentrates that contain lingering residues.

Cold Water Hash is a Solution to the Rising Distaste for Solvent-Based Extracts

The idea of finding lingering solvents in cannabis leaves a bad taste in the mouths of many consumers, even if most state regulators have deemed them safe and placed acceptable limits on them. This shift toward cold water extracts reflects a natural shift in the market, as some consumers appear to prefer “pure” concentrates over “potent” ones.