Anti-Solvents: Our take on this hot button issue

Anti-solvent crystallization appears to be a hot topic, so we decided to share our thoughts. The most basic definition is “a solvent in which your compound is less soluble.”

When looking at hydrocarbons, the shorter the chain, the less soluble the compounds are in your solvent. Propane may therefore be considered an anti-solvent to butane. When you extract with butane, this makes the crash possible due to a drop in solubility through temperature loss, as upon injecting to a low pressure zone such as butane at 16 PSI (or lower), the propane auto-refrigerates to a temperature based on its pressure.

For example, liquid propane at 20 PSI has a temperature of -21°C, which is roughly the temperature at which THCa begins to crash out of propane due to the cold conditions.

If you are already extracting with a propane-dominant blend, a more appropriate definition is a cold crash. THCa typically starts to crash out of propane at -20°C and colder because of the chain length. Butane needs to be much colder, closer to -40 to -60°C, and pentane needs to be even colder, such as -80°C. Time also becomes a factor as longer chains typically take longer to crash than shorter chains.

A better example of an anti-solvent is using acetone for crashing waxes out of ethanol extract. It is instant and works at room temperature.