Hey Natalie! I’ll take over for Benna here. The 90% alcohol works well for plants that are very water-rich and juicy, this helps to dilute the alcohol percentage significantly in the final product, and also resin-rich herbs as you said. Perhaps the motherwort doesn’t have as high of water content to warrant the 90%. It may be better with around 60-70% alcohol. After you press the motherwort tincture, I’d suggest re-evaluating and then slowly adding water to get it to a place where it isn’t so harsh. You won’t know exactly what percentage this mixture is, so go slow. As long as your tincture ends up being 30% alcohol or higher, it will be preserved.
For the future, you can dilute before mixing your alcohol with your herbs.
Here are the directions for diluting high percentage alcohol:
A simple equation to calculate this:
-% Spirits needed = (Desired Alcohol % ÷ Alcohol Content of Spirits) x 100
-So if diluting high-proof alcohol (90%) to 40%, this would look like: % Spirits needed = (40 ÷ 90) x 100 = 44.4% alcohol, and the remaining 55.6% would be water.
From here, you can calculate how much this translates into mL, depending on how much menstruum you want to make. For 100 mL, this would look like 44 mL alcohol, and 56 mL water.
The equation again to achieve a 60% alcohol:
-% Spirits needed = (60 ÷ 90) x 100 = 66.7% alcohol, and the remaining 33.3% would be water.
I know you said you had a bunch of resources, not trying to bombard you with more but these ones are trusty!
Different tincture making guidelines:
Also, the books, ‘The Herbal Medicine-Maker’s Handbook’ by James Green provides you with a chart that suggests the % o alcohol to use for various plants and their parts.
Also, ‘Making Plant Medicine’ by Richard A. Cech et al. is a great resource.
I hope all of this helps. Let us know if anything else comes up!