Let’s dive into the underlying characteristics of the ultimate cannabis dry room. 60/60 gets thrown around as something everyone shoots for, but why? The secret sauce behind every killer cannabis dry room is a combination of two basic ingredients: Equilibrium Moisture Content (EMC) and Vapor Pressure Deficit (VPD)
Equilibrium Moisture Content 💧
When you dry your cannabis, you are pulling water out of the buds and into the surrounding environment… until you’re not. EMC is the magic point where your buds have the same moisture as the air around them, which means they stop drying. This concept is most intuitive from the cure process: cannabis in a sealed container will, after some time, hold the same moisture content.
The key to understanding the cannabis dry process is that drying is a balance between the moisture in your plant and the moisture in the air. If the environment is constantly changing, the bud moisture won’t ever equilibrate.
Vapor Pressure Deficit ☁️
VPD itself is a measurement of the difference between the amount of moisture in the air and how much moisture the air can hold when it is saturated. The VPD value helps quantify how quickly the surrounding environment will “pull” water out of your buds. Higher temperature and lower humidity mean higher VPD (buds drying quickly), and low temperature and higher humidity mean lower VPD (buds drying slowly).
The Cannabis Dry Goldilocks Zone: 60/60 🎖️
So what does this mean for drying rooms? Check out the VPD = 0.8 curve (orange/red), in Figure 1 below. If the drying room can maintain a VPD of ~0.8, your cannabis will be in the optimal moisture range (10-14%) in 7-10 days. Additionally, the moisture will be slowing down in days 7-10 because you are coming closer to the EMC, which buys you more time to tweak things.
This VPD brings you right into the goldilocks zone: slow enough to avoid uneven drying, and fast enough to avoid mold! A VPD of 0.8 can be made with an environment of 59°F and 55 % humidity. So the 60/60 golden rule is founded in the science of drying!
Figure 1. Temperature and Humidity effect on Cannabis Dry time. Jim Faust Laboratory, Clemson University. Cannabis Research Coalition.
Avoiding Swings ⛔
Let’s take a quick look at what poor environmental controls do to your dry process.
This dry data in Figure 2, which was monitored via the ZONE system, had daily swings in temperature and humidity that ranged from 77°F and 46% humidity (~1.7 VPD) to 58°F and 61% humidity (~0.64 VPD). Because of the drastic difference, the moisture (green curve in Figure 2) goes through repeated cycles of quick drying and slow drying. Imagine you are bouncing between the red curve and green curve in Figure 1.
This inconsistent process burns off terpenes, exacerbates negative microclimate effects, and makes your time to dry vary by about 4 days!
Figure 2. A poorly controlled Cannabis Dry
Measuring where it Matters in the Cannabis Dry 💡🌿
The environment that we discussed throughout this cheat sheet is the environment that the drying cannabis experiences. While the HVAC on the ceiling will say it is regulating at 0.8 VPD, drying dogbones or buds that have been packed together create a dynamic environment that can create radical shifts in climate. It is of the utmost importance that you measure the plants directly where they are drying.
The ZONE sensors solve just this problem. They measure, temperature, humidity, and the moisture of the drying bud from the environment the cannabis experiences. The ZONE dry monitoring system brings your Cannabis Dry right into the modern world with unprecedented view of what is happening where it matters most. Ready to discuss how data-driven drying can revolutionize your cannabis dry operations?