Last updated: November 19, 2021

What Does Purging Mean?

In the cannabis industry, purging refers to the process used to remove any residual solvents, especially butane, from the cannabis extract. The end-result is ideally a solventless cannabis extract that is safe and pure.

Some cannabis connoisseurs argue that it is nearly impossible to purge 100 per cent of a solvent from an extract.

In addition, not all butane hash oil (BHO) undergoes purging before it hits the market. If the oil is not purged, the chances are good that it will continue to contain a small amount of butane.

Purging is a very important process that is typically required when making pharmaceutical quality cannabis extracts.


Maximum Yield Explains Purging

Purging cannabis extracts involves using a vacuum to heat the product at less than atmospheric pressure. The molecules will heat and release the gas. Once the pressure is turned down, the gas is released and the vacuum oven pulls it from the chamber. Vacuum ovens are the ideal way to purge BHO, but the ovens are costly.

Small amounts of BHO can be purged using a water method and a vacuum pump instead of a vacuum oven. With the water method, the BHO is extracted directly into a dish that is floated in hot water. The hot water purges and evaporates the butane from the BHO. A vacuum pump is then used for the final purging process.

The purging process can be avoided if a less harsh solvent is used during the extraction process. For example, water hash or dry sieve hash is made without the use of harsh solvents. Likewise, CO2 extraction does not require purging.

In some cases, such as alcohol extraction, the purged solvent (the alcohol) and be recovered and used again. This is considered solvent recovery, which is somewhat related to purging.


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