Classic texts: Journals: AJP 1871. How to calculate alcohol strength.
Tinctures
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Propolis.
Henriette's herbal blog: It's just a blend of various resins, and can be tinctured or made into resinous oils much like other resins.
Tinctures.
Henriette's herbal blog: Fresh vs. dried herb tincture strength.
Absorption.
Henriette's herbal blog: There's a reason that alcohol tinctures are so popular.
Making tinctures.
Henriette's herbal blog: Tincturing is fairly easy.
Lemon verbena and percolating.
Henriette's herbal blog: Percolating a lemon verbena tincture.