I think I have been confusing about an aspect of drying and I am hoping someone can help explain this to me.
My initial assumption was that when drying the flower will eventually reach equilibrium with the relative humidity. So if the RH of my drying space is 60%, the flower will eventually reach 60% humidity and stay there. The temperature I thought only impacted the rate of drying - higher temperature means a faster dry. It’s easier to change humidity than to change temperature in my drying area, so I would set the humidity to be at 60%. However, there were times when after jarring I found the flower to be at a lower humidity than 60%.
I’ve also heard of using vapor pressure deficit for drying, which is calculated using temperature and RH. I had better drying results setting my humidity to a specific VPD than a specific RH. In trying to understand this, I found agricultural articles that show the Equilibrium Moisture Content of final product depending on both RH and temperature. With a fixed RH, a higher temperature results in a lower moisture content in the final product when equilibrium is reached.
Does this align with others’ understanding? It is still a bit counterintuitive to me.
Honestly it seems like the old standard of 60°f 60% humidity is apparently NOT optimal
I believe the science is still out on what exactly is best. My opinion though, storing flower at 60% RH is kinda moist, i find the smokability of stored flower is best around 50-55% RH.
I dry weed in my home so there’s no way I can get any room of my house as low as 60°f so as far as that goes, i just dry in the coolest room of my house with the heater vents in that room shut.
With relative humidity, it is always dependent on temperature.
If you have a room that is at A temp and X humidity, and you lower the temperature to B without changing anything else in the room, the measured relative humidity will change to Y without you doing anything.
This explains better than I can about the relationship between temp and humidity. Perhaps that will be helpful? It does seem counterintuitive, but basically warm air holds more moisture, so the relative amount looks different. 50% of a 50 gallon tank is quite a different amount than 50% of a 300 gallon tank. Anyway, like I said, this is better than my stuff.
Equilibrium humidity of the actual thing will still be affected this way (as I understand it), because the humidity of the container that you’re measuring is still affected by the temperature of the space it is in.
I understand that relative humidity depends on temperature, but I think the assertion I am reading is that holding RH constant and increasing temperature results in a drier product. So if you dried at 60% RH and 70 degrees F it would be drier than 60% RH and 60 degrees F. This is the counterintuitive part to me.
The warmer air has more capacity for holding moisture, and thus it can pull more from the grains. So the gas tank analogy from above, using purely hypothetical numbers:
If 60°F is a 200 gallon tank, and it is 60% full of water, there is 80 gallons of available space.
If 70°F is a 300 gallon tank, and it is 60% full of water, there is 120 gallons of available space.
If you have 100 gallons of water that needs to be absorbed, you will never get it fully dry if you are trying to put all of that water into 80 gallons of space.
I do not know if that is helpful or makes it more confusing. Apologies if the latter!
(I stared at the chart for a while, also confused, because it is counterintuitive, then revisited the link because I felt I must be missing something)
That is helpful, thanks. So really VPD is the measure to use for equilibrium, because it represents the capacity of the air for holding more moisture. An environment held at .8 VPD will eventually result in the same level of dryness every time, regardless of the temperature. The recommendation of 60/60 is around .75 VPD, drying at 75 degrees and 75% humidity is also .75 VPD, so either will result in the same end dryness (ignoring the risk of mold at higher rh). Except the corn chart doesn’t align with that, it shows a higher moisture end product at 75/75 than at 60/60. Maybe there is some additional factor.
I feel like at least some element of the situation is that they’re measuring corn, which has different membranes and whatnot. Grain is inherently going to behave differently than flower or leaf material.
Beyond that, your guess is as good as mine! I’m curious to see what else you figure out.
edited to add: Oh, actually, that might just be an element of “yeah, they are the same (proportionally), and one of them is existing at higher humidity”. Because if you look at the chart, higher humidity correlates to…higher humidity, across the board.
