Case hardening is a term borrowed from timber and food drying. When the surface of a bud loses water faster than the core can supply it, the outer tissue dries and tightens into a shell that slows further drying. The bud feels crisp outside while the centre is still moist.
In practice
Symptoms: buds that feel jar-ready after only a few days, then go spongy and damp once sealed; jars whose equilibrated RH climbs far above 65% overnight; dense colas with a damp core when cut open.
Causes: warm, dry drying rooms; fans blowing directly on buds; wet-trimmed small buds on racks in low humidity; dry periods of only 3-5 days.
Prevention: slow the dry, about 15-21 °C (60-70 °F) and 55-62% RH, with gentle indirect airflow, aiming for roughly 7-14 days. Leave more leaf and stem on (dry trim, whole-plant hang) in dry climates.
If it happens: jar the buds and burp often, or spread them on a tray in a humid room for short sessions, letting the moisture even out. Check closely for mould.
Don't confuse with
- Over-drying: dry all the way through.
- Sweat: moisture moving outward in a jar, part of a normal cure.
- Mould: a possible consequence of case hardening, not the same thing.
The relative humidity of the air in a sealed container once it has stopped exchanging moisture with the material inside; ERH / 100 equals the material's water activity.The dense, elongated cluster of flowers that forms at the end of a stem or branch; the main cola tops the leader.A dark, ventilated space where freshly harvested cannabis is dried under controlled temperature, humidity and gentle airflow, usually for 7-14 days.Pest and disease prevention by changing how the crop is grown, such as humidity, airflow, spacing, watering and cultivar choice, so pests and pathogens struggle to establish.Relative humidity is the water vapour in air as a percentage of what it could hold at that temperature, so the same RH dries plants differently at different temperatures.Trimming sugar leaves after buds have dried, leaving the leaves on during the dry to slow it and protect the bud.Drying an entire harvested plant upside down, uncut except at the base, so the large stem mass slows the dry.Drying cannabis below the target water activity (under about 0.55), leaving buds brittle and harsh, with lost terpenes; rehydrating does not restore them.A drying rule of thumb: dry cannabis at about 60 °F (15.5 °C) and 60% relative humidity so buds dry slowly over roughly 10-14 days.Moisture moving from the inside of dried buds to their surface after jarring, making them feel damp again; normal early in a cure but a warning if excessive.A 0-1 measure of how freely available the water in a material is; for dried cannabis flower the accepted range is about 0.55-0.65 aw.
