Drying Hemp Using “The Wisconsin Method”
One of the new commercial hemp drying techniques gaining attention as an industry best practice is the Wisconsin method. First developed as a means to dry hops (Humulus lupulus), this practice is equally beneficial for hops’ close botanical relative, hemp. Learn the steps involved in this hemp drying process and decide whether the benefits of using it might improve the aromatic quality of your product and give your company the competitive edge it needs.
1. Create Your Hemp Drying Box
The first step is to create a container to hold your hemp drying racks. You can use a variety of construction materials, including hard plastic, drywall, or even plastic sheeting, as long as the final structure is airtight. Your drying box can be located in any building with a power source to accommodate an electric fan and dehumidifier.
Your box should be just large enough to hold the amount of product you pick in one day, and the leaves should be evenly spaced from each other. The benefit of this method over other hemp drying techniques is that limiting your batches to a single day’s harvest prevents uneven drying and the chance of losing leaves to decay.
2. Establish Air Flow
Attach hoses to the box to create an air intake and exhaust system powered by a fan. Ideally, fresh air should pass evenly over all the hemp leaves before exiting the box. You may have to experiment to find the ideal placement of plants to minimize air recirculation and over- or under-drying of plants packed too close or too far apart.
If you live in a humid climate, or if plants are drying more slowly than you would like, you may consider placing a heat source directly behind your fan. A caveat to this technique is the fact that heat lowers the concentration of naturally occurring aromatic compounds called terpenes. For this reason, experts in hemp drying techniques recommend never exceeding 37 degrees Celsius.
3. Switch to a Dehumidifier
When to turn off the ventilation system and switch to a dehumidifier inside the box depends on the amount of moisture you can tolerate in your finished product. Hops growers, for example, usually stop at 30 to 40% moisture content and switch to using a dehumidifier inside the drying box until the buds reach 10%.
When subjected to continuous airflow, plants in a drying chamber usually lose 20 to 40% of their moisture within 18 to 24 hours. However, you will need to experiment to find the optimal amount of time required for your unique drying box and the climate where you live. When completely dehydrated, you are ready to empty your hemp drying racks and make room for the next day’s harvest.