How to make a freeze dryer for cannabis

Published Jul 13, 2019 12:44 p.m. ET
iStock / Joanna Wnuk

If you are just learning how to cure marijuana, the options are nearly endless, and the results from each technique will vary significantly from the next. Luckily, with rapidly advancing technology, there are always new and exciting methods to dry cannabis, with many of the most recent making leaps and strides as they create user-friendly options that help to preserve more cannabinoids and terpenes than we ever thought possible. One of the latest trends to hit the industry is freeze drying, and it’s making waves as it proves to be one of the best, fastest, and most gentle method of curing cannabis thus far.

What is freeze drying?

Freeze drying is just one way to cure freshly harvested marijuana plant flowers, and it works by drawing all the moisture out of the plant materials slow enough, that the flowers maintain the same size and shape throughout the process. The extremely cold temperatures used can pull out the moisture, which is stored in a water trap, and since it happens so slowly, the water can act as a temporary dissipating skeleton for the bud flowers, which is what helps to maintain the buds form. This is done by using pressure to convert the water into vapors that are easily drawn out using a vacuum.

What are the benefits of freeze drying cannabis?

  • Fast working. From the moment you start the machine to the time the buds are ready to be packaged or consumed, the entire process takes only 24 hours to complete.

  • Minimal cannabinoid and terpene loss. Freeze drying, when done properly, actually helps to strengthen some of the sought-after components that are produced by cannabis plants like THC, CBD, and terpenes. The average loss of those elements with this process hovers around 1%.

  • Faster Trimming. Since the flash freezing makes the outer leaves brittle and crumbly, the process of trimming can be reduced up to 80%. This is also the only method that allows for clean trimming using machines.

  • Larger buds. Since the structural integrity of the cannabis bud flowers is held in place by the water as it is drawn from the chamber, the marijuana colas will look the same when they are finished curing, as they did in the moments before they were placed into the dryer. This results in larger, and fluffier buds.

  • Preserved colors. With all other methods of drying cannabis, the hue of the plant materials themselves will fade and darken. This can turn the brightest, most colorful buds, into a dull and less than an exciting end product. If there is one thing we know for sure, it’s that consumers appreciate an aesthetically pleasing bud.

  • This drying method can be used at any point, including either before or after trimming.

  • Natural minerals, vitamins, and oils remain in-tact. This is especially important for consumers who might be eating cannabis flowers.

  • Freeze dried buds are easy to break apart for joint rolling or device packing, so there is no preparation needed before customers can use weed if it’s been cured this way.

  • How to make a freeze dryer for weed (and use it)

    Figuring out how to make a freeze dryer for cannabis can be full of trial and error, but once you get the seals in place, and have a working machine, the rest of your job will be easy as pie. You can use many different types of materials in place of those that are listed here, as long as they can hold up to the pressure and cold for an extended period of time.

    You will need:

    • 2 2-quart vacuum chambers
    • 1 2 gallon-stainless steel pot with lid
    • 1 ¼ inch flare union
    • 1 ⅝ barb splicer
    • 3 meters (or less) of ⅝ inch tubing with braided reinforcement
    • 4 large 1-inch thick Styrofoam sheets
    • Glue (school glue or any spray adhesive)
    • 1 cooler filled with dry ice slabs
    • Denatured Ethanol (approximately 1-liter)
    • 1 high-quality vacuum gauge
    • 1 2-stage rotary vane vacuum pump
    • 1 carpenters knife
    • 1 package of JB Weld
    • 1 small hose clamp


    1. The first thing that you will need to do is create a protective barrier that can line the cooking pot to help keep it cold. To do this, measure out squares that allow for 3-4 inches of Styrofoam on each side, and then trace out the base of the pot to make them into sleeves.
    2. Feed them one by one onto the bottom of the cooking pot, until it is entirely covered. Then cut three more squares without holes to act as a base. This will protect the surface that the freeze dryer is set on.
    3. Double check the sleeves fit, and once you are confident the pot will fit comfortably, you can glue all the pieces together. This helps as it creates a seal that will keep the frigid temperatures in.
    4. Now cut one more piece of Styrofoam by measuring the size of the vacuum chamber inside of an outer circle that fits the 2-gallon pot. It will help to hold the chamber in place, as well as to keep the cold air inside.
    5. Feed the chamber sleeve over the top of it and set it into the pot. Now you can measure and remove a small square from the sleeve, that will allow you to drop in dry ice as needed.
    6. Attach the union to one of the chambers and use it to hook up the vacuum gauge.
    7. Remove the vacuum gauge that came with the second chamber and use a ⅝ bit to widen the hole enough to fit the splicer.
    8. Use the JB Weld to secure the splicer in the hole.
    9. Allow the JB Weld sufficient time to dry completely, and then hook up the rubber hose by sliding it over the splicer and clamping it into place.
    10. Now you will want to make a few more insulating sleeves for the chamber that you have installed a gauge on, just like you did with the pot, including three layers for a base.
    11. Once you are finished gluing the last of the insulation pieces together, it is time to put your freeze dryer to good use.
    12. Fill the 2-gallon cooking pot approximately ¾ of the way with denatured alcohol and drop several pieces of dry ice in through the window. Once you begin adding dry ice, the alcohol will bubble for a few minutes, but as the temperature of the liquid drops that will slow down so that you can safely add more throughout the process.
    13. Place the cannabis plant materials inside of the chamber that is sitting in the cooking pot and seal the lid.
    14. Turn on the vacuum pump, and watch the magic happen. You will need to add additional dry ice at least every two hours over the next 24 to maintain the ideal temperature.
    15. After 24 hours, it’s time to shut everything down and assess the results. If you have anything other than perfectly cured bud flowers, then you likely have a leak somewhere in the system. At that point, you can go over all the connections and joints with some JB weld until the issue is resolved and try again.

    How to store marijuana after it has been freeze dried

    Once you have freeze dried your cannabis, if you haven’t already, it will need to be trimmed before it can be tucked away safely into storage. Since buds that have been dried with this method end up firmer than others, you might think that it can be stored in a baggie, but we highly recommend against that. Instead, you should invest in some high-quality resealable glass jars that will keep the marijuana from bouncing around and turning into powder.

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