Short answer
Kief is the loose resin that falls off cannabis or hemp flower. It builds up in the bottom chamber of a three-piece grinder. The resin is a mix of trichomes, the tiny glands on the flower surface. Trichomes hold cannabinoids and terpenes. Hemp kief carries CBD and small amounts of THC. Cannabis kief carries THC, often 40 to 60 percent by weight.
What trichomes are
Trichomes are glandular hairs on flower, leaves, and stems. Glandular trichomes make and store cannabinoids such as CBD and THC plus volatile terpenes. They look like small crystals under light. The heads break off when the plant is handled, which is why kief shows up in grinders and collection trays.
Kief vs hash and vs flower
Hash is kief pressed with heat and pressure. The pressure ruptures trichome heads and forms a solid block. Kief stays a powder. Kief is more concentrated than the flower it came from. Cannabinoid and terpene content per gram runs higher because plant material is screened out.
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THC and CBD numbers
US law defines hemp as cannabis with 0.3 percent THC or less on a dry weight basis. Lab reports list THC and CBD as a percentage of sample weight. Kief concentrates what the flower held, so a hemp strain at 0.2 percent THC can yield kief that tests near or above the 0.3 percent line. Read the certificate of analysis for each batch.
How to collect kief
- Three-piece grinder with a mesh screen. Common screen sizes run 50 to 150 microns. Smaller holes give cleaner kief and lower yield.
- Dry sift screens. A stack of 220, 160, and 120 micron screens separates plant matter in stages.
- Cold. Put flower in the freezer for 10 to 20 minutes before grinding. Cold trichome heads snap off with less plant dust.
- Yield. Dry sift returns about 5 to 15 percent of the starting flower weight.
Decarboxylation
Raw kief holds acidic cannabinoids: CBDA, THCA, and others. Heat removes the acid group. A common oven setting is 220°F for 30 to 40 minutes. After decarboxylation, CBDA becomes CBD and THCA becomes THC. Decarb before adding kief to oil, butter, or tinctures. Inhaled use applies heat during use, so no oven step is needed.
Storage
Keep kief in an airtight glass jar. Store it away from light and heat, at 65 to 77°F. Kief is a fine powder with more surface area than flower. It loses terpenes and oxidizes faster than the flower it came from. A batch can change color and smell in a few months at room temperature.
How to use kief
Sprinkle it on ground flower, vape it alone, or press it into hash with a heated tool. For edibles, decarb first, then mix into fat. Fat carries cannabinoids. Water does not.
Labeling
Kief sold in stores should list CBD and THC content per gram, batch number, and test date. Ask for a certificate of analysis from an ISO 17025 lab. A COA that shows only CBD and no THC value is incomplete.