Making Alcohol Based Tintures

Marc: solid matter in a tincture; herbs
Menstruum: liquid in a tincture; the alcohol and water

Weight-to-volume tinctures are made by carefully considering two aspects of balance: the balance between the weight of the marc and the volume of menstruum, and the balance of alcohol and water in the menstruum. This balance is written as a ratio and a percent, like 1:2 75%, which is basically a shorthand recipe of the tinture.
With weight-to-volume tinctures you can be sure what the dosage is and replicate the recipe within a predictable margin

Tincture Ratios
The ratio of marc to menstruum is written as a mathematical ratio, like 1:2, 1:3, etc. That means for every 1 part of marc you use 2 parts (or 3 parts, or 4 parts) of menstruum. We measure "parts" in ounces.
Marc (herb) is measured using ounces of weight, like on a scale
Menstruum (alcohol) is measured using ounces of volume, like on a measuring cup
So to make a 1:2 tincture, we will use 1 ounce of marc on a scale for every 2 ounces of menstruum in a measuring cup. If you have more than 1 ounce of marc, multiply the weight of the marc by the 2nd number in the ratio. For example:
If I have 5 ounces of an herb and I want a 1:2 tincture, I will use 10 ounces of menstruum, because 2 x 5 =10.
If I have 5 ounces of an herb and I want a 1:3 tincture, I will use 15 ounces of menstruum, because 3 x 5 =15.
if you make a tincture at the less-than-ideal ratio, nothing bad is going to happen and your tincture will still be useful-it wil be a little stronger or weaker.
Dense plant parts like roots and barks are tinctured at a farther ratio like 1:3 or 1:4, because they weigh more.They can soak up a lot more menstruum into that fiber, which will make your marc stick out of the top if you don't put in enough.

Understanding Alcohol Concentration
The second aspect of balance of a weight-to-volume tincture is the balance between alcohol and water in the menstruum. We write the alcohol content as a percentage, with the remaining percentage out of 100% as water: 40% means the menstruum is 40% alcohol, 60% water.
The concentration of store-bought alcohol is easy to figure out because it is half of the proof, which is written on the label. For example, 80 proof vodka is 40% alcohol, and the remaining 60% is water. 40% - 50% is a good standard range for tintures and does well with most dried herbs. Absolut Vodka makes a 100 proof I find good results with.

Weight-to-Volume Tincture Recipe
You will need: Dried medicinal herb, grain alcohol; kitchen scale; measuring cup; clean canning jars; labels; you also might want a mortar & pestle or food processor.
1. Decide what ratio you want to use, between 1:2 and 1:6
Example: I'm choosing 1:3
2. Decide what concentration of menstruum you want to use, between 40% and 95%
Ex: 75% (now we have 1:3 75%)
3. Finely chop or crush herbs and weigh them on your kitchen scale using the ounce marks. This number is the 1st number in the ratio (the 1)
Ex: My lemon balm weighs 4 oz on the scale
4. Multiply the weight of your herb by the second number. This number is the volume of menstruum you need.
Ex: 1:3 is the ratio, I have 4 oz of lemon balm. 4 x 3 =12 oz menstruum
5. Multiply the total volume of menstruum by the concentration of alcohol you want. This number is the volume of alcohol (if the alcohol is grain alcohol). If the alcohol is not grain alcohol, you are probably using it at it's bottled strength so you don't need to add water.
Ex: 12 oz menstruum x 75% = 9 oz alcohol
6. Subtract the volume of alcohol from the total volume of menstruum. This is how much water you need.
Ex: 12 oz menstruum - 9 oz alcohol = 3 oz water
7. Put it all together!
Ex: 4 oz by weight of herbs, combined with 9 oz grain alcohol and 3 oz water
8. Measure the alcohol and water in a measuring cup, using the ounce marks
9. Put the herbs in the glass jar and pour the water and alcohol over them. Don't forget that herbs take up space when you choose the jar!
10. If the menstruum doesn't cover the herbs, mash them down. If they still don't submerge, add 1 more "dose" of menstruum
Ex: our tincture is 1:3, so we can make it 1:4 by adding another 4 oz menstruum (3 oz alcohol and 1 oz water) for a total of 16 oz menstruum at 75% alcohol
11. If the herbs still don't fit, or if you don't want to lower your ratio (say, because you're doing a root tincture and you're already at 1:6), put the whole works in the food processor
12. Clearly label with plant, ratio/ alcohol.
13. Let sit for 6 weeks or more in a cool, dark place, shaking regularly
14. Strain the marc out of the tincture using a mesh tea strainer. Then squeeze the strained marc in a cheese cloth to extract the last, strongest part of the tincture.
15. Store in a clearly labeled glass jar or bottle in a cool, dark place. Tinctures last for years.