Winterization is a process when we dissolve oil in a polar solvent like ethanol and subject it to subzero temperatures for extended periods of time. As the temperature of the solution drops, the solubility of hydrophobic, non-polar compounds (plant waxes) become reduced and they coagulate, forming globs which float in the solution. These globs are then filtered out using varying pore-size screens.
Now the easier-to-read version. When we preform primary extraction – there is usually quite a bit of other biproducts that get extracted other than cannabinoids and terpenes. The most common byproducts are plant waxes (called plant lipids or fats). These are fatty acids which are used to make soaps and other products like lotions, etc. Where distillation is concerned, we want to rid our crude of as much fats as possible because they have a similar boiling point to cannabinoids and will usually carry over into the final product. This will result in cloudy or “waxy” distillate when held up to the light. Distilling unwinterized crude will also noticeably reduce the final yield. The process we put our crude through to remove these compounds is called winterization.
Imagine when you put Vodka in the freezer – it doesn’t turn into ice like water. This is because the freezing point of alcohol is much colder ( -173.5F or -114C for ethanol) nearly 100x the temp for water! You would need a hardcore scientific freezer or liquid nitrogen reactor to make ethanol ice cubes. Plant waxes have a low freezing point just like water, which allows them to precipitate out of alcohol when frozen for a period. Lipids don’t like cold temperatures when they are suspended in a hydrophilic medium. Have you ever put chicken or beef broth into the fridge and looked at it the next day? Chances are there are fatty lillypads floating around in your soup after 8+ hours in a chilly environment. This is essentially what we are trying to achieve with our crude before we filter out all the solids. Ideally for a thorough winterization, you want to go as cold as possible but typically -40C is adequate. Remember also that fats also coagulate at different saturation levels so multiple freezing stages with filtration in between is highly recommended for this process to be thorough.
Filtering out the Waxes
After the alcoholic solution is allowed to sit in the cold for a while – the hydrophobic compounds will reveal themselves to the naked eye in the form of globules. The globules of frozen waxes are then removed through a process of filtration through a series of varying-size screens using a Büchner funnel or another filtration device. The results are quite interesting to watch! What was before a murky miso-soup-like concoction of fatty crude and ethanol transforms into a crystal-clear liquid and we are one step closer to distillation. There are many more things to consider during filtration such as filter mesh size, filter media, etc. We will cover this plus provide an SOP for proper winterization in subsequent articles.