Kief holds 20 percent to 60 percent THC by weight. Flower holds 15 percent to 25 percent. The trichome heads carry the cannabinoids, and kief is trichome heads plus a small amount of plant matter. A lab report on kief depends on three things: the screen size, the source flower, and the storage history.
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What kief is
Cannabis flower grows resin glands called trichomes. Each gland has a head and a stalk. The head holds THCA, THC, CBD, terpenes, and other compounds. Growers separate the heads from the plant with dry screens or ice water. Dry screens run from 75 microns to 150 microns. A 75 micron screen passes heads and few leaf pieces. A 150 micron screen passes heads, leaf bits, and stem bits.
Leaf and stem carry little THC. They add weight. A sample with more plant matter tests lower per gram.
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THC ranges by product
- Dry sift kief: 20 percent to 50 percent THC
- Ice water hash: 40 percent to 60 percent THC
- Pressed hash: 40 percent to 70 percent THC
- Flower: 15 percent to 25 percent THC
These ranges come from published lab data and state testing reports. A single sample can fall outside them.
THCA and decarboxylation
Fresh kief holds THCA. THCA does not cause intoxication. Heat removes a carboxyl group and converts THCA to THC. An oven at 240 degrees F for 40 minutes converts most of the THCA in a thin layer of kief. Heat above 300 degrees F boils off THC. Total THC on a label equals THC plus THCA multiplied by 0.877.
Dosing
A standard edible serving in states with rules is 10 mg THC. Kief at 50 percent THC holds 500 mg of THC per gram. A 10 mg dose is 20 mg of that kief, or about 0.02 gram. Use a milligram scale. Kief varies from batch to batch, so weigh each dose.
Storage
THC oxidizes to cannabinol (CBN) with heat, light, and air. Store kief in an airtight glass jar. Keep it dark and below 70 degrees F. A sample stored for two years tests lower in THC and higher in CBN than a fresh sample.
Labels and testing
States with legal markets require potency tests. Washington requires THC testing on licensed cannabis products and sets label rules. Labs use high performance liquid chromatography (HPLC) to measure cannabinoids. Lab results carry a margin of error. That margin runs 10 percent or more on a kief sample.