Short answer
Heat in rosin pressing runs from 160 F to 220 F. Flower needs the top of that range. Hash and kief sit lower. Press time runs 30 to 120 seconds. Pressure runs 300 to 1,000 PSI at the puck. Heat softens the resin so pressure can push it through a mesh bag. Temperature also sets the color, the yield, and how much terpene survives the press.
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Temperature by starting material
- Flower: 180 F to 220 F. Bags 90 to 120 micron. Yield 15 to 25 percent.
- Dry sift: 170 F to 200 F. Bags 37 to 90 micron. Yield 40 to 60 percent.
- Bubble hash: 160 F to 200 F. Bags 25 to 45 micron. Yield 50 to 70 percent.
These ranges come from commercial press operators. Home presses run the same numbers. The plate temperature and the puck temperature differ. A 200 F plate holds the puck near 170 F to 190 F during a 90 second press.
What more heat does
At 220 F, flower gives up more rosin per gram. The oil runs thinner and comes out darker. More terpene leaves the puck as vapor. The result is a higher yield with flatter flavor.
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What less heat does
At 180 F, the puck gives up less rosin. The oil runs thicker and comes out lighter. More terpene stays in the oil. The result is a lower yield with stronger aroma.
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Pressure and time
Most press gauges report pressure at the platen, not at the bag. Puck pressure is higher. Small bags on large plates take more force. Too much pressure bursts the bag and pushes plant matter into the oil. Too little leaves rosin in the puck. Time follows heat: a 220 F press finishes in 60 to 90 seconds. A 180 F press needs 120 seconds or more.
Cannabinoids and heat
THCA converts to THC at 220 F to 240 F over 30 to 60 minutes. A press at 200 F for 90 seconds converts little. Most rosin tests as THCA with a small THC fraction. THC boils at 315 F. Terpenes such as myrcene and limonene boil above 300 F, but they leave plant material at lower temperatures because they are volatile.
Curing after the press
Cold cure holds rosin at 40 F to 60 F for 3 to 14 days. Warm cure holds it at 100 F to 120 F for 30 minutes to a few hours. Curing changes texture from a sap or shatter into a budder or badder. Texture does not change potency.
At the store
Rosin labels list cannabinoid and terpene content. They do not list press temperature or press date. Ask the staff for the batch date. Rosin has a shorter shelf life than butane hash oil. Store it near 60 F to 70 F, in the dark, in a sealed jar. Refrigeration slows terpene loss. Room temperature above 80 F speeds it up.