(use food grade Glycerin)
Glycerin based tinctures have a shorter shelf life than alcohol based tinctures. They can sit on the shelf but I prefer to refrigerate mine. Vegetable glycerin has nearly no affect on blood sugar or insulin and is very low in calories (4.3/gram). It does have a very sweet taste but that just makes your tincture more palatable.
Use the amount of cannabis that you desire for potency. I use eight (8 ounces) ounces of good shake to one (1-gallon) gallon of glycerin. Put your shake into a clean blender or whatever method you have for turning it into a powder. Place powder and glycerin into a crock pot on the lowest setting. If it gets too hot, you will kill the properties you are trying to extract. You want your mixture to be as warm as possible without boiling. Leave the tincture to heat anywhere from 4 hours to 3 days. Test the mixture every four hours. You decide when it is done. Do not over heat! Glycerin really holds the heat so do not burn yourself.
If you do not have a crock-pot, you can place the herb in a clear, sealed jar in a warm, sunny spot and accomplish the same thing in about four weeks. Do not forget to shake the jar every day.
When ready, strain the mixture through cheesecloth, the THC has been extracted and the tincture is ready to use. It will take a lot longer to strain the glycerin mixture than the alcohol mixture.
The best way to store a tincture is in a dark colored bottle (amber, cobalt blue, dark green). Glass bottle only.