I’ve seen conflicting advice on different herbal recipes when it comes to adding vodka to alcohol tinctures. Some say to add vodka to cover the herbs; some say to add vodka to cover with an inch or so of clear alcohol atop the herbs. Further complicating the issue is the fact that some recipes mandate the use of more expensive 100 proof (50% alcohol by volume) vodka, while others seem to imply that the cheaper 80 proof/40% alcohol vodka is fine. What gives?
What does alcohol in tinctures do?
It has a couple of basic functions. The first one should be obvious from the alcohol tincture’s other name: ethanol/water extraction. We use tincturing because there are some desirable compounds in an herb that aren’t soluble in plain water, and the ethanol gets it out for us. This is also part of why garbling is important–the ethanol needs to have access to the compounds we’re looking for.
Alcohol’s other function in a tincture is for preservation: we want tinctures to last a long time, especially since we often devote a large quantity of herb to the making of a given quantity of tincture. I’ve seen figures suggesting that alcohol concentrations above 37.5% should have adequate ethanol content to prevent fermentation and rot.
So if we’re working with vodka that’s either 40% or 50% alcohol, why does it matter? Furthermore, why do we need the extra inch? Do we always need it?
Can you figure it out?
As a hint, I think we’d get different results trying to make a tincture of dried cinnamon bark than a fresh dandelion tincture.
I think it’s about the water content in the herbs, and that the inches thing is a red herring–or, at least, a rule of thumb. If the herb we’re using has very little water content, as in the cinnamon example, the 40% alcohol might be fine because the herb contains almost no water to dilute it. But with a jarful of fresh dandelions, there’s a lot of water still locked up inside the dandelions, and it’s not a stretch to imagine that it might dilute even 50% alcohol down below that critical 37.5% threshold.
Remember that people say to dry your herbs carefully after washing? Same story: every drop of water on a dandelion leaf is working to dilute our alcohol down below 37.5%.
So I think the extra inch of vodka isn’t about excluding air (unlike in fermentation where the extra inches of brine are needed to create an anaerobic environment), but rather about ensuring that there’s enough alcohol in the jar to handle any excess water that comes out of the herb.
What do you think?