Winterizing is the term for redissolving a non polar extraction in a polar solvent and then lowering the temperature low and long enough for the non polar plant waxes to precipitate out of solution, so they can be removed by filtration, to turn a raw oleoresin extract into an Absolute.
The non polar plant waxes are marginally suspended in the polar alcohol and when the temperature goes down and the ability of the alcohol to hold solute in solution, the first thing to drop out is the non polars. In point of fact, the waxes would precipitate out of solution all by themselves at ambient temperatures if given enough time.
Here is a jar of BHO dissolved in ethanol, which simply sat on the shelf for a month:
Extract after precipitation
We typically use about a 10:1 ration of alcohol to essential oils and chill them about 48 hours at -18C/0F, but have accomplished the same end at -50C in about XX hours.
If we are going to winterize an extract, we typically wash it out of the collection pot with warm ethanol, so that when we remove the ethanol post filtering, we will also remove the residual LPG.
Winterized and ready for filtration
Filtering through coffee filter
Plant waxes that were removed by winterization
Above we are using a regular coffee filter and conventional funnel. Here is how we fold he filters to do so:
Lap as necessary to fit smaller funnel
A step up is to use a commercial coffee filter and holder, also available from your local restaurant supply. That's also where I got the chinoise strainer to the right, which I use for rapid rough filtration:
Commercial coffee filter in holder and ultra fine Chinois strainer
For larger batches we use vacuum filtration to speed things up, and typically use a #1 Whatman filter in a Buchner funnel.
Vacuum filtration using a Buchner funnel and Whatman # 1 lab filter