When we talk about the humidity of cannabis, we’re often speaking in relative humidity (RH) measurements:
RH refers to the amount of water vapor in the air compared to the maximum amount of water vapor the air can hold at a specific temperature.
Think of it like a sponge. A dry sponge can absorb a lot of water. As it gets more saturated, it can’t hold as much additional water. Similarly, as air gets colder, it isn’t capable of holding as much additional moisture.
So, if you have a jar of plant material stabilized to a certain RH and you change the temperature, the RH reading will change even though the actual amount of moisture in the jar hasn’t changed.
The Impact on Cannabis Curing
Curing is a critical process that involves slowly drying and moisture-stabilizing the cannabis to make it safe for long-term storage, which also improves the flavor and smell by breaking down compounds like chlorophyll.
During this process, it’s essential to maintain a specific RH level to prevent mold and mildew growth while allowing the plant material to cure properly. Understanding the relationship between temperature and RH is necessary for getting your ideal cure in your specific lung room and storage environments.
One common way growers are affected is when curing in a cooled environment (like in a refrigerator/cooler) then bringing the cannabis back up to room temperature for consumption. When bringing cool cannabis back up to room temperature, you will likely notice a slight decrease in the RH reading.
This doesn’t mean that the cannabis has suddenly become drier. It simply means that the warmer air can now hold more moisture, so the relative humidity reading drops.
We highly recommend you keep the temperature in your lung room as stable as possible throughout your entire curing process to avoid any confusion.
Applying the Concept
The difference in RH is surprisingly significant at varying temperatures:
- Cannabis cured at 55°F to 62% RH will become 36.6% RH at 70°F
- Cannabis cured at 60°F to 62% RH will become 43.8% RH at 70°F
- Cannabis cured at 65°F to 62% RH will become 52.2 RH at 70°F
Additionally, the chart below shows how cannabis cured at 65°F changes when exposed to different temperatures. You can see that cannabis cured at 65°F to 60% RH will change to 42.7% RH when brought up to 75°F.
You can play around with more RH and temperature conversions at https://www.markusweimar.de/en/humidity-calculator/
