How to vacuum purge BHO?
BHO extractions are becoming more and more popular today. In this Blog, we have already seen different BHO extractors and explained their functioning and advantages and disadvantages when making marijuana oil.
In this post we will focus on how to purge the solvent from this appreciated liquid gold, which offers us new experiences and opens new horizons in the world of marijuana concentrates and their recreational and medicinal uses.
Once the BHO extraction (with purified butane gas) is done, we have to purge any remaining trace of butane present in the extract. First, we will make a light purge with a bain-marie (water bath). During this process, we can observe how a large number of bubbles are formed and then burst, releasing the gas retained. In this first purge we remove an important amount of gas from our BHO, but it is not enough to get a marijuana oil 100 % clean of impurities.
In these pictures you can see the steps followed before the vacuum purge, so you can see the state of the BHO after this first and important bleeding performed with bain-marie (water bath). Always purge the gas next to a window or directly in an open area.
In the following picture, taken a few minutes later, we can see how almost all the gas used for the extraction has evaporated. However, the remaining resin concentrate still contains butane, so we must vacuum purge it to leave it completely free from impurities.
At this point, we can pop the remaining bubbles with a dabber to release the maximum amount of gas contained in the extraction.
One of the easiest ways to know if the BHO still contains gas is, after the first water bath purge, taking some BHO with a dabber and approaching a flame to the oil (Warning: do not approach any flame or spark before or during the water bath purging process, and do not approach any flame to the Pyrex tray until all gas has been purged). If we see or hear small sparks coming from our BHO, then our extract still contains gas and must necessarily be vacuum purged to ensure a final product without any trace of gas. Vacuum purging is advised by all professionals in any extraction with solvent.
More examples of gas purge of BHO in water bath
To correctly vacuum purge our marijuana oil we need the vacuum extraction kit. Ours is composed of:
- A Rothenberger vacuum pump
- 2 Oil canisters for the maintenance of the vacuum pump
- 1 Connecting pipe to connect the vacuum pump and the desiccating chamber
- 1 Vacuum purge chamber with stopcock
Once we have all the necessary equipment ready, it’s time to set it up and start vacuum purging our BHO extractions.
The vacuum compressor for the BHO purge
This is an essential element to purge out the gas from our oil, since it is the power source that will generate the air suction in the vacuum chamber.
The Rothenberger vacuum pump has a final vacuum of up to 34 bar with a pumprating of 170 L/min (6 CFM). Motor rating is 3440 RPM with two-stage rotary vane pump to get greater efficiency. Oil capacity is 330 ml.
This vacuum pump has enough power to remove all small gas bubbles trapped in the marijuana oil in a very effective and fast way.
Technical features of the Rothenberger Roairvac 1.5:
- Weight: 11.5 Kg
- Final Vacuum: 34bar
- Pumprating: 170 L/min – 6CFM
- Voltage: 230v
- Oil Tank: 330ml
- Motor: 2-stage rotary vane pump
- Motor rating: 3440 rpm
- Standard Connector SAE 1/4″
- Compatible Connectors: 5/6″ – 3/8″
Vacuum connecting pipe
This connection tube is another of the three elements necessary to perform the vacuum purge. It’s composed of a rigid body coated with a protective plastic layer. This tube features high pressure resistance during the vacuum process, without getting blocked by the suction power generated by the pump.
It’s important to emphasize that this tube must be specifically designed for the use with vacuum, otherwise it’s possible that it bends or twists without properly performing the vacuum extraction.
At both ends, we find two adapters with a screw to connect the pump with the vacuum chamber without air leaks for a rapid and effective purge.
Vacuum purging chamber with stopcock
This is the third indispensable element to purge our BHO. This acrylic vacuum chamber has a stopcock and great resistance to implosion. This tool is composed of two semi-spheres, being one of them the base and the other one the lid with the stopcock, which should be open to allow the vacuum process. Inside the lower, inner semi-sphere, we find a support plate where we have to place the BHO that we want to purge.
How to vacuum purge a BHO extraction
We have all the necessary equipment to purge the BHO that we have obtained with an extractor, an unbleached coffee filter, gas free of impurities and of course, the high grade raw material: buds full of large resin glands.
The first step is to connect the required equipment. The ideal is taking advantage of the liquid state of the BHO after the first purge – performed with bain-marie – to ease the removal of the gas bubbles that are trapped inside the oil. The more solid the oil, the harder will be to remove the impurities contained in the concentrated cannabis resin.
We recommend using low temperatures – around 35ºC – for the first purge (water bath) to remove the maximum possible amount of butane without affecting the organoleptic properties of the oil, since aromatic terpenes evaporate faster as temperatures rise.
Once all devices are ready to use, put the BHO on a baking paper or silicone pad inside the vacuum chamber. Now, and after checking that all components are correctly connected, we can turn on the vacuum pump.
The pointer of the barometer will always mark the pressure inside the vacuum chamber; when it reaches zero, the vacuum is created and the BHO starts purging.
After reaching the vacuum phase we can see almost immediately how the oil slowly transforms its appearance, developing craters caused by the emergence of bubbles created from the pressure of the compressor. These bubbles will burst and crystallize simultaneously during all the vacuum process taking form of a crystallized sponge, with an exponential increase of its volume.
At the time that we stop the vacuum we can observe how the appearance of crystallized sponge decreases and returns to its initial state, but being less fluid than before starting to purge.
We should repeat this process approximately 4 times (or more) for about 10 to 20 minutes, always remembering that this period of time can vary depending on different factors, such as the amount of butane present in the BHO after the first water bath, the amount of BHO to purge or the room temperature (the lower the temperature, the more difficult to remove the bubbles).
As we have no way to know the exact period of time required to completely remove all butane, we must use as reference the BHO itself. When its appearance doesn’t change at all and it stays in the form of a crystallized sponge even under vacuum, we have successfully performed the purging process and we can proceed to consume or store our oil.
The BHO obtained can have different shapes and textures. If it looks like a compacted volcanic rock we can save it as is because it doesn’t contain humidity and can be stored for a long time. On the other hand, if it remains in the form of a crystallized sponge, we can compact it and give it a round shape to store it easier in nontoxic and non-adherent silicone containers or in an essence jar with protection against UVA rays, so it can be consumed when you want.
Other samples and forms of BHO
It is important to highlight and remember that during a BHO extractions we are using butane gas, and we must be extremely careful when we deal with any volatile product that can be set on fire with a simple spark produced by a lighter, by the brushing of one metal with another metal, by heat sources, electronic devices, certain types of clothes, etc.
Remember that performing these extractions in an open place, preventing any butane accumulation, is absolutely essential. We also want you to remember that gas is heavier than air, so it will always stay below air and can settle on the floor if you don’t take the above mentioned precautions. You should always avoid basements since that the gas can be accumulated and explode.
So, if you enjoy making and using your BHO, always take extreme care during the process !