You winterize butane extracts. The butane has a polarity that will grab fats, waxes, and lipids, but not chlorophyll. Iso and everclear will grab chlorophyll and other stuff that will make your extract dark. So for winterizing you take your bho and place it in everclear and dissolve it, I recommend not heating up your solvent to dissolve the extract it will darken it. Once your extract is dissolved place it in the freezer for a minimum of 24 hours. You will notice some thing precipitating and falling out, these are the fats waxes and lipids. You will then want to filter these out, I would put a cup with a filter rubber banded in it, in the freezer with the extract solution to get the filter below freezing as well, this will help keep the waxes fats and lipids solid when filtering. Then when you are satisfied pour your solution into the filter and close your freezer, you make have to do this is steps if you have used more solvent. Once the solution has filtered through, remove the filter and pull your solution from the freezer. Then you will need to purge out the everclear, a thin layer method is suggested, pour your solution into a pyrex dish with a fan gently blowing over it, depending on the amount this will take 24 to 48 hours. you will notice white pulls of milky liquid forming this is normal it is water and will evaporate off.
If you have anymore questions feel free to ask...