I’ve read all about it, and keep seeing people talk about water leftover...? Can anyone explain? Want to winterize with grain alcohol then evap in double pyrex (like when blasting) and then purge in vac with some heat. Will that work?
Removing most of the alcohol does not need much heat if you blow air over the surface. I use a round bottom flask and an aquarium air pump. I only need to warm the flask to about 40C. It helps to ensure the final product is light honey colored.
You do end up with some water at the end. That depends on your ethanol. Most ethanol is about 95% alcohol meaning you have 5% water. In my runs I use 120mL ethanol leaving about 6mL of water at the end. Purging at the end with a vacuum pump gets rid of the rest of the water. Personally I start using the vac pump when I get to the last 20mL on solvent (if you change the vac pump oil every run it wont kill the pump).
The azeotrope containing ethanol and the 5% water are the last to go, along with any atmospheric humidity the alcohol has picked up from contact with air. One trick to get rid of most of, before using heat to evaporate off the rest, is to stick the shallow dish with the mixture in it, into a freezer to make the concentrate more solid, and then you can pour or blot off much of the water mixture.