Evaporating the base solvent (ethanol) from your tincture will leave behind a potent concentrate of the botanical used to make your tincture. If working with cannabis or hemp tincture, the concentrate that is left behind will be a potent oil containing the THC or CBD that was present in the original cannabis plant material.
There are a number of different ways to evaporate away the ethanol from your tincture. Ethanol will naturally evaporate out of solution if left unattended for a long enough period. By changing the variables of temperature, air flow, or air pressure (think vacuum) the speed of evaporation of the ethanol can be greatly increased. Modifying the variables listed can be done independently, or in cooperation, and doing so however incorporates trade offs that should be considered.
If adding heat to the system, the speed of evaporation will be significantly increased, however issues of safety as well as the necessity to closely monitor the progress of the evaporation are introduced. Applying too much heat to the tincture can decarboxylate and then scald/burn the evaporated concentrate producing an unusable final oil. Also, there are safety concerns with combining heat sources and ethanol vapors, and one should never mix heat and ethanol vapors without strongly considering the safety of the overall system and process including flame risk and ventilation of the fumes/vapors created.
Changing the air pressure of a closed system containing an ethanol tincture will lower the temperature at which the ethanol will naturally evaporate (the boiling point of the liquid). This can have the benefit of increasing the speed of evaporation while eliminating the safety concerns of a heat source, as well as reducing the possibilities of burning/scalding a batch of oil. However, creating a sustained vacuum can be an expensive endeavor requiring specialized equipment designed for that sole purpose. Vacuum ovens and vacuum pumps require regular maintenance, have a high up front cost, and consume vacuum oil as part of their normal operation.
Increasing air flow however has the benefits of increasing the speed of natural evaporation, without requiring special equipment, and without introducing the safety concerns presented with adding a heat source. Of all of the potential methods presented to increase the speed of the evaporation of the tincture, increasing the air flow is the method that we recommend based on the being the safest method. Also, because no heat is introduced to the system, there is little-to-no risk of the final concentrated oil being ruined/burned/or over decarboxylated. Finally, increased air flow systems do not require any special equipment, materials, consumable oils (like vacuum pumps), and require no supervision while the evaporation is occurring.
How to build your own air flow evaporation system.
Building your own air flow evaporation system is simple, easy, convenient, and cost effective. When using increased air flow to evaporate the ethanol contained in a tincture, the two most important variables are 1.) Air flow amount (typically measured in SCFM or standard cubic feet per minute) and 2.) Surface area of the tincture exposed to the air flow.
Introducing AVA. A.V.A. stands for Alcohol Vanishing Apparatus
The following design for AVA has been used to evaporate about 100 gallons of tincture over the past 5 years. The design for AVA is presented free of charge for people to use to build their own, or to make modifications upon for their specific need.
To build your own AVA you will require the following raw materials. These materials are all available at your nearby big box store or local hardware dealer. There is no special ingredient or material that makes the system work, all components can be obtained easily or substituted by some other material that will perform the same function.
1.) Two (2) wire bookshelves. The shelves used in the image measure 24″ wide by 12″ deep x 24″ tall. Two are used to create a cube design that can easily hold 4x trays of tincture, however I never load more than 2x trays in at a time. Wire construction is important as it provides the right amount of structure for holding trays of tincture, while also allowing for adequate air flow. Plastic shelving should be avoided as it does not provide enough air flow without compromising structural integrity of the shelf (it will start to bend under the weight of the tincture after repeated use). The rigidity of the wires also provides for convenient mounting locations for the box fan.
2.) A 20″ box fan. The standard kind with 3 speeds, though I never use any speed over #1 (the slow speed). A smaller fan will work too, but I’ve found that using a properly sized big fan reduces the risk of having a jet stream effect reducing the overall ability of the system to evaporate. The 20″ model coupled with the 24″ x 24″ foot print of the book shelves creates an even flow of air everywhere inside the unit.
3.) Clear or semi-transparent plastic sheeting. The function of this sheeting will be used to wrap your book shelves into an air tight fume hood. Clear or semi-transparent is recommended because it allows in light so that you can see the trays of tincture inside the unit while the evaporation is progressing. Conversely dark black plastic wrap, will work just fine for containing air flow, but will render the inside of your AVA into a dark cave that will need additional lighting to be able to see inside. Source at least 100 square feet of clear plastic sheeting to cover an AVA measuring 24″x 24″ x 24″.
4.) Furnace Air Filter. 20″x 20″ model to fit the size of your box fan. This component will filter any foreign particles contained in your room air from your evaporated concentrate. Opting for HEPA filtration might be an added benefit depending on the quality of the room air in your local environment, however not a hard requirement.
5.) 6″ Flexible Dryer Duct Hose. This is the flexible silver “hose” that is typically run from the back of a standard household dryer to the out door vent. The standard dryer duct hose measures 4″, seek out the next available size up at 6″. How much length should you plan on? You will run at least 2x of these hoses out to the nearest window to vent the ethanol vapors outdoors. If you can source 8″ duct work, even better. Your box fan is capable of creating way more air flow than the duct work can likely vent, so increasing the amount of duct vents will increase the efficiency of your AVA. My current design uses two (2) 6″ duct’s with about 12 feet of length per hose. If you are limited to sourcing 4″ duct hoses only, plan on enough length of hose to run three (3) ducts out of the top of your evaporator.
Other materials needed for construction of your AVA:
Wire ties – These are used to secure your book shelves together, and to mount the box fan to the bottom of the wires.
Duct Tape – Used to seal off any areas where air might escape vs being vented through the duct work. Have at least 2x rolls handy. White is recommended, but any color will work. White duct tape blends in easily with the semi-transparent plastic wrap, keeping the job looking tight and professional.
Air Conditioner Weather Stripping – This foam is used to ensure an air tight seal between the box fan and the book shelf bottom. Any weather stripping or foam will work here, but the Air Conditioner variety available at local hardware stores is soft and supple enough to provide a good seal without too much fuss or precision.
Velcro – Used to seal the door. Source the “industrial variety” which comes in 2″ wide strips and is especially durable for repeated opening and closing.
Foam or Wood for mounting duct work in window – Any material will do here, the function is to adequately hold the exhaust duct work in a way that can be mounted in a window while providing some kind of back draft seal. All windows are shaped differently, personally I have had success with a rectangle of 2″ blue insulation foam cut to 12″x 18″. In this rectangle I have cut 2x 6″ holes which fit my 2x 6″ dryer hoses. When performing an evaporation, the 12″x 18″ foam rectangle fits the opening of my window perfectly, preventing any back draft of ethanol vapors back into the house. The snugness of this fit means winter installations will not result in snow or cold air back draft affecting the room temperature either. If foam is unavailable or undesirable, a wooden setup with similar holes will perform the same function.
How to construct your own AVA (Alcohol Vanishing Apparatus)
Step 1.) Assemble the wire book shelves and position them next to each other so they form a cube. These wire book shelves are typically provided with 3x shelves that can be mounted at various heights using the provided mounting hardware. The recommended mounting heights are as follows: Mount the bottom most shelf at 8″ from the bottom feet. This height provides enough room to mount the box fan while also allowing adequate air flow into the fan. Mount the middle shelf approximately 12″ from the bottom shelf. The middle shelf will be the primary location for holding the trays of tincture for evaporation. This shelf can be mounted lower rather than higher if it will make for a more convenient location for loading and observing the trays of tincture. Mount the 3rd shelf at the top most available spot on the shelf. The top shelf will serve only as structural support for mounting the flexible duct hoses later in the assembly.
Step 2.) Once the location of the shelves is finalized, fasten the two book shelves together tightly using the wire ties.
Step 3.) Cut the air conditioner weather stripping into 20 inch strips. Cut four (4) strips 20″ long each.
Step 4.) Mount the box fan to the bottom of the wire book shelves. Do this by weaving the wire ties through the grate of the box fan and then through the wire metal shelving. Before tightening the wire ties, insert the air conditioner weather stripping foam in between the box fan and the wire shelf, along the perimeter of the fan. Pull the wire ties tightly to secure the fan to the wire shelf and to compress the foam weather stripping proving an “air tight” flow of air up through the bottom most wire shelf.
Step 5.) Wrap the outside of the wire book shelves with plastic wrap. Wrap the top, sides, and back of the book shelf, but leave the front unwrapped at this time. Use duct tape to seal any creases or folds that may allow air flow to escape.
Step 6.) Using duct tape, apply to the perimeter of the front that has been left open. First, tape the left side and the right side, creating a 2″ wide perimeter of duct tape. Then tape the top and the bottom. Next, apply Velcro directly to this perimeter of duct tape.
Step 7.) Using scissors, cut a 24″ x 24″ square out of the plastic wrap. Apply Velcro to the perimeter of the square. Note that the Velcro side chosen for this application should be the opposite side of Velcro chosen in step 6. Mount this square onto the front opening so that the opposing sides of Velcro attach to each other. This is the door, when it’s time to open, peel from the top down about half-to-3/4 of the way down. When ready to close, firmly press the two sides back together to create an airtight resealable door.
Step 8.) Measure the 6″ dryer duct hose to the appropriate length and cut 2x pieces. Looking top down, and starting from the front left corner, measure 8″ to the right and 12 inches to the back. Mark a dot using a Sharpie and cut a 6″ hole centered on this mark. Next, from the right front corner, measure 8″ to the left and 12 inches to the back. Mark a dot using a Sharpie and cut a similar 6″ hole centered on this mark. Mount the dryer hose over each cut out by threading a wire tie through the support wire of the duct hose through the wire of the top shelf. Use adequate duct tape to create an air tight seal between the plastic wrap and the duct work. If using 4″ ducts, create 3X holes evenly spaced to allow for even air flow.
Step 9 – Mount the hoses into the foam window insert.
Step 10 – Done
When you are ready to run you evaporation.
Step 1.) Follow these directions to make a quick wash tincture.
2.) Obtain the largest aluminum baking tray you can find. I recommend visiting your local dollar store that typically carries the large turkey sizes aluminum pans. These disposable pans are not only the largest I am aware are available, but also about 3″ deep.
3.) Obtain a Teflon sheet from SlickSheet via Amazon.com. Cut you Teflon sheet into a 20″ strip. This will permit 2x strips per roll with 8″ left over for the decarboxylation stage after evaporation.
4.) Using binder clips, secure your Teflon sheet to your aluminum tray. This takes some practice to get the sheet to fit just right.
5.) Place your lined tray into your AVA. Don’t add the tincture yet, you will add the liquid next.
6.) Pour your tincture into the line tray once placed in your AVA. Filling the tray after it’s already in AVA will save you from spilling the liquid while attempting to move a filled tray, trust me.
7.) Close up the velcro door.
8.) Turn your box fan onto setting 1 (low).
9.) Wait. This process will take about 100 hours to evaporate 128 fl oz of tincture.