Cannabis enthusiast and student of the art of solventless extraction
The moisture content of cannabis flowers is an important factor to consider when sourcing the best starting material for pressing flower rosin. Either too much moisture or too little moisture will negatively impact the extraction. Using flowers with just the right moisture level is key to maximize both yield and overall quality. Relative humidity is a good indicator of the amount of moisture in flowers.
How can we measure the relative humidity of cannabis flowers? The best way to measure relative humidity, or RH, is to place the flowers in a sealable glass or stainless steel jar with a digital hygrometer. After a couple hours the reading on the hygrometer will stabilize, giving you the relative humidity of the air inside of the jar (measured as a percentage). Although the hygrometer is actually measuring the humidity of the air in the jar, that is directly correlated to the moisture content in the buds.
The optimal relative humidity for pressing cannabis flowers is 60-65%.
Yield will be reduced when pressing flowers that are too dry. Overly dried flowers will actually reabsorb the rosin as it’s being produced. Very dry flowers are like a sponge that capture some of the rosin, soaking it in and preventing some of it from flowing out of the bud and onto the parchment paper.
Flowers that are too wet will impart excess moisture into the rosin, apparent with a crackling sound when the rosin is dropped onto a hot nail for dabbing. Flower that’s very wet will also pop and hiss during extraction as moisture escapes with heat and pressure between the rosin pressing plates.
Flowers that are either too dry or too wet are both problematic for rosin extraction. So what if your flowers are not within the 60-65% range of relative humidity?
If they’re too wet, simply letting them dry out in the open air is fine. Keep them out of direct light and in a dry place. Retest the flowers in a sealed jar with a digital hygrometer to verify when they are ready to press.
If the flowers are too dry, you can rehydrate them with a technique referred to as the damp paper towel method. Just wet a piece of clean paper towel using clean water and keep it inside of a sealed jar with the flowers. Don’t let the wet paper towel directly touch the flowers. You can hang it over the top edge of the jar and let it hang down inside, sealing the lid over it.
Read more in our article How to Rehydrate Dry Cannabis Flower For Rosin Pressing.
Even the highest quality of cannabis flowers won’t press well if they are either too wet or too dry. Make sure to check the moisture by measuring relative humidity and adjust as needed until they’re in the 60-65% relative humidity range.
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FREQUENTLY ASKED QUESTIONS
How do you measure the moisture in cannabis flowers?
Measuring the relative humidity in a sealed jar containing cannabis flowers is a good way to measure the moisture content in the flowers. You can use a digital hygrometer inside the jar to get a reading of relative humidity.
What is a hygrometer?
A hygrometer is used to measure relative humidity. Digital hygrometers are small and relatively inexpensive, and great for measuring moisture in cannabis flowers.
What is the ideal moisture/humidity level for pressing cannabis flowers for rosin?
60-65% relative humidity is the ideal moisture level for pressing cannabis flowers.
What if you press cannabis flowers that are too dry?
Overly dry cannabis flowers will reabsorb rosin when they’re pressed, leading to reduced rosin yield.
What if you press cannabis flowers that are too wet?
Pressing cannabis flowers that are too wet imparts excessive moisture in the rosin, reducing overall quality.