2-way humidity packs are thin pouches that contain water vapor, natural salts, and food-grade thickeners which help regulate humidity levels within airtight spaces. Traditionally used by cigar aficionados to preserve moisture levels inside humidors, 2-way humidity packs have been adopted by the cannabis industry to keep flowers at just the right humidity. Relative Humidity, or RH, is a measurement of moisture in the air (given as a percentage), and helps us aim for the right amount of moisture within cannabis flowers.   

But why is moisture important? For both smoking and pressing rosin, there is an ideal range of humidity that keeps cannabis flowers from becoming too dry and brittle, or too soft and spongy. Overly dry cannabis flowers burn too quickly and don’t yield their maximum potential of rosin. Flowers that contain too much moisture don’t burn properly and invite mold growth, and also produce rosin that contains excessive moisture. 

Therefore, it’s important to ensure that cannabis is stored in an environment with the right humidity, otherwise the moisture levels within the flowers will fluctuate outside the ideal range. We can use the RH inside a sealed container with cannabis as an indicator of moisture within the flowers. Placing cannabis flowers in a mason jar with a digital hygrometer is an easy way to measure RH. 

60-65% RH is a good target for cannabis that’s destined for both rosin production and smoking. 

When Does Cannabis Need To Be Rehydrated?

This means that rehydration is a corrective measure, rather than preventative. The best case scenario is to keep flowers within the proper moisture levels from harvest until usage, and to avoid the need for active adjustment. But if your flowers drift outside of this ideal moisture range, you can actively rehydrate the bud. 

Typically, 2 way humidity packs are used for preserving levels of hydration, rather than drastically altering moisture levels. For example, humidity packs are normally employed during storage, not during the initial drying and curing phase of the flowers. There are several manufacturers of these humidity packs, Boveda being the most popular. 

Potential Downside of 2-Way Humidity Packs

Terpene content is one of the main metrics that determine the overall value of a certain batch of cannabis. The most significant potential risk that 2-way humidity packs pose is speeding up the loss of volatile terpenes. Terpenes naturally break down and dissipate over time, but certain factors (like heat) are known to expedite the process. It’s thought that 2-way humidity packs, such as Boveda, can do the same, and cause more of those valuable terpenes to waste away. 

Despite a lack of scientific proof that 2-way humidity packs negatively impact terpene content, or impart a certain offputting taste and smell onto the flowers, many growers and extractors have claimed to see diminished results after using humidity packs like Boveda. This has been accentuated when humidity packs are used shortly after harvesting, to actively quicken the curing process. But rushing the cure can have its downsides. 

One argument is that if you’re doing everything correctly, you shouldn’t need 2-way humidity packs. At best, these are handy shortcuts to manage a less-than-ideal situation. However, that’s not what Boveda has to say… 

Boveda claims that its 2-way humidity packs are actually terpene shields, proactively preserving terpenes thanks to a monolayer of moisture which coats trichome heads. In this view, humidity packs not only adjust moisture levels, they defend against terpene loss through evaporation. 

That said, a quick look around Reddit and other forums where cannabis connoisseurs gather, and you can find plenty of accounts of Boveda packs impacting cannabis for the worse. This seems to be the case especially when 2-way humidity packs are kept with overly-wet flowers, in an attempt to speed up the drying and curing process.  

If you need less moisture (lower RH) to further dry out the flowers, leave the storage container open for a period of time each day. This can range from 5 or 10 minutes to even longer, depending on the moisture inside. 

So What’s The Best Way To Rehydrate Cannabis?

While 2-way humidity packs may not exactly be cannabis killers, they may not be worth the risk if there are alternatives. And thankfully, there are. 

Using pieces of fruit to rehydrate flowers can also have unintended consequences. Read more in How to Rehydrate Dry Cannabis Flower For Rosin Pressing.

Soak the stones in clean RO water and they are ready to go. Try to avoid direct contact with the cannabis flowers if possible. You don’t want any of the flowers to get too wet by coming into contact with the saturated stone. 

Using clean paper towels and RO water is a safe alternative, if you don’t have terracotta stones available. 

Conclusion

The best case scenario is to keep cannabis in the 60-65% relative humidity range as the flowers go into storage after drying and curing. Controlling the drying room to ensure that the flowers don’t overly dry is the first step, followed by proper storage. Super dry buds don’t yield well for rosin, and they’re less than ideal for smoking in this condition as well.    

Fortunately, if cannabis gets too dry, there are other ways besides 2-way humidity packs to bring them back to the right level of moisture. Humidity packs are best employed for keeping flowers at the correct humidity over a period of time, rather than changing the moisture in a drastic way. 

Read more about drying and storing cannabis in What Is the Best Environment for Hang Drying Cannabis Flowers? and Best Ways To Store Cannabis Material for Extraction.

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FREQUENTLY ASKED QUESTIONS

What is a 2-way humidity pack?
2-way humidity packs are thin pouches that contain water vapor, natural salts, and food-grade thickeners which help regulate humidity levels within airtight spaces.

How do you use a humidity pack?
Humidity packs are used to help keep cannabis within the 60-65% relative humidity range after the flowers have dried and cured. 

What is the downside with using humidity packs?
Some people have noticed issues with smell and taste after using humidity packs, especially when the flower is still very wet and the packs are used to actually absorb the excess moisture. This approach should be avoided. It's thought that humidity packs can potentially decrease terpene levels, although this hasn't been proven. 

What are the alternatives to using humidity packs?
To rehydrate cannabis, you can use a wet paper towel or terracotta rehydrating stones soaked with RO water.  

Can you use humidity packs to help dry cannabis that's too wet?
Some people who have tried this approach report that it affects the taste and flavor of buds in a negative way. It's better to let flowers naturally air dry than try to speed up drying with humidity packs.