Winterizing & Polishing of BHO Extracts

Winterizing & Polishing of BHO Extracts

Butane, a popular solvent used in cannabis extraction, makes beautiful concentrates called Butane Honey Oil (BHO).  A “winterization” process with food grade ethanol (95% or higher) can be used to clean and polish your BNO concentrate.  Winterizing will eliminate most of the remaining butane and remove undesirables like fats, lipids and waxes.

Step 1: Ethanol Bath

Mixing a butane extract with >95% ethanol is a very efficient way to purge excess butane and remove undesirables from the extract. The BHO extract can be mixed with 10-20 volumes of ethanol and warmed to 40-50°C. Using too little ethanol may result in leaving desirable components (e.g. cannabinoids and terpenoids) with the undesirable components (e.g. chlorophyll and plant waxes). The solution must be stirred until the extract is completely dissolved and the bubbling has ended.


Subjecting this ethanol suspension to freezing temperatures encourages the undesirables to coagulate and solidify.  These solutions must be butane-free and in tightly sealed containers, This step can be accomplished in the domestic freezer in 48 hours or with dry ice over about 3 hours.  For optimal results, the solution should not be disturbed during the cooling phase.


Step 3: Removal of Coagulated Undesirables by Filtration

The undesirable components (e.g. chlorophyll and plant waxes) are quite easy to remove with filtration. Unbleached coffee filters are acceptable for this task, but finer grades of filter paper and Buchner funnels will catch more of the undesirable material.


Step 4 (Optional):  Reprocess Collected Undesirables by Repeating Steps 1-3

The undesirable by-product of the first filtering (retained on the filter paper) can be combined with clean ethanol, and steps 1-3 can be repeated to retain more of the desirable material (e.g. cannabinoids and terpenoids).


Step 5: Purge Ethanol from the Filtrate

The wash is simply a combination of cannabis oil and ethanol. To isolate the cannabis oil for use as a concentrate, the ethanol must be removed. This is best achieved by evaporation of the ethanol with a rotary evaporator. Other methods are more dangerous because of the flammable nature of ethanol.

 Author Dr. Craig Davis