The Truth About Vapor Pressure

September 21, 2022

Guest Blog with Sharkmouse Farms

Relative humidity is simply the percentage of water in the atmosphere before it becomes fully saturated to the point it can't hold any more and condenses. The amount of water that can be held is greatly impacted by the temperature. The higher the temperature,  the more water can be held as vapor. This is why RH, in itself is insignificant in the curing process other than its importance as part of an equation in understanding vapor pressure.

The moisture in your flower is working within a system trying to equalize the pressure between that moisture,  and the moisture in the atmosphere.  Dew point is the measure  of how cool the air must be to reach saturation, the point where dew begins to form! By cooling the air, we reduce the dewpoint, thereby reducing the amount of water the atmosphere can hold.

This means, at a lower dewpoint,  the vapor pressure will be lower, drawing less water out of your flower and avoiding drying out essential oils, cannabinoids and terpenes. The ideal vapor pressure to achieve proper aW  (or water activity) in your curing flower is 0.62kPa. 62% rH and 65.35 F. This makes a dewpoint of 52 °F.

"Burping " is a means of replacing the air inside the jars that have reached ERH (equilibrium relative humidity, or when the air and flower neither draw moisture or condense, equal) in a fresh cure, that vp is drawing moisture out of the flower until the jars reach equilibrium. We do this until the ideal aw is achieved, then hold at equilibrium in a perfect aW of 0.6-0.65 aW= equilibrium rh/100 (62%/100 😉)62% 65.35f Dewpoint  52°f

During cure, your flower will be metabolically active in a process that involves the continuous enzymatic degradation of starches and sugars; while moisture levels are maintained to mitigate the biological possibility for pathogenic and bacterial growth below viable levels.

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