Last updated on July 22, 2026 · Originally published April 23, 2017
Quick wash ethanol, or QWET, is a technique for using ethanol as an extraction solvent while limiting ethanol’s biggest drawback: its tendency to pull chlorophyll, waxes, and other unwanted plant material into the extract along with the cannabinoids. The approach is deceptively simple — keep the ethanol very cold and the contact time short — and it works because both cold and speed reduce how much of that undesirable material the solvent dissolves before the wash is separated from the plant.
Why Ethanol Needs the Trick in the First Place
Ethanol is effective as a solvent because its molecules contain both a polar hydroxyl group and a small non-polar carbon chain. That mixed character lets it dissolve cannabinoids efficiently, but it also lets ethanol recover chlorophyll, pigments, sugars, waxes, and other components of the plant matrix. The result can be a dark, vegetal-tasting crude that requires additional refinement. (For the underlying chemistry of how a solvent’s polarity determines what it extracts, see our explainer on solvent polarity in cannabis extraction.) QWET is the technique built to limit that broad co-extraction.
How the Cold-and-Quick Approach Works
Two things do the work: temperature and time.
In a typical QWET process, both the ethanol and the cannabis are chilled well below freezing — often to around −20°C or colder, sometimes with dry ice — before they come into contact. Low temperature changes the solubility of plant constituents and slows the transfer of material from the biomass into the solvent. Many waxes, pigments, and other unwanted co-extractives are therefore recovered less readily, while cannabinoids remain sufficiently soluble for a brief wash. The exact balance depends on temperature, contact time, agitation, solvent composition, and the condition of the biomass. This differs from winterization, which uses cold ethanol after extraction to precipitate waxes and lipids that have already entered the crude, so they can be filtered out.
Time is the second lever. Rather than the long soaks used in some tincture methods — which give ethanol hours or days to leach out everything, chlorophyll included — QWET keeps the plant material in contact with the solvent only briefly, often on the order of a few minutes. The wash rapidly dissolves cannabinoids and terpenes from the exposed trichome resin and is then separated from the biomass before slower co-extractives accumulate. The resulting solution is filtered, and the ethanol is removed — typically recovered for reuse in commercial systems — leaving a lighter-colored, cleaner extract than a warm or prolonged soak would generally produce.
The Tradeoff Worth Knowing
QWET involves a genuine balance, but it’s more nuanced than “colder is cleaner but lower-yielding.” Cold and brief extraction can reduce cannabinoid recovery if the process isn’t optimized — yet low-temperature ethanol can still achieve high recovery under the right conditions. One peer-reviewed study reported THCA extraction efficiency of roughly 84% at −20°C, nearly 98% at −40°C, and approximately complete recovery at room temperature, with values calculated relative to a reference sample — showing that temperature does not affect yield in a simple linear way.
Processors therefore balance recovery, selectivity, throughput, and downstream-refinement needs. QWET is often favored when flavor and clarity matter, while some operations pursue a more exhaustive extraction and rely on later refinement, including winterization, when maximum recovery is the priority. The right approach depends on the intended product and the workflow that follows extraction.
For comparison with hydrocarbon extraction, see T&T’s complete guide to BHO extraction.
Originally published 2019. Updated July 2026 to correct the explanation of why cold ethanol extracts more selectively, add peer-reviewed data on how temperature affects cannabinoid recovery, and connect the process to the underlying solvent-polarity chemistry.
