When I wrote my previous book Making Tinctures: Beyond the Folk Method, I viewed glycerin, as many herbalists do, as a solvent equivalent to alcohol and treated it as such in making glycerites. However, in the years since that book was published, I have worked more with glycerites, as well as have done more research. As a result, I have discovered that there are many considerations including solubility and preservability which require another look at how to use glycerin in tincture formulas.
To explain how to use glycerin instead of alcohol in a formula for a tincture requires some understanding of what are the differences in properties between alcohol, water, and glycerin, and how each interacts with specific herbal constituents.
Following are some of the practical conclusions from both my research and my experience that define why and how I now apply glycerin to my own practice and that you may find useful.