This is a good method for extracting water-soluble constituents, especially those sensitive to heat. The most common dose for powders is the amount that you can pick up on the tip of a dinner knife. Or you can boil the plant materials in honey or store-bought syrup and then strain through cheesecloth. Syrup is especially useful for administering medicines to children. Like other alcoholic extracts, tinctures will keep for a long time.
Homeopaths use very dilute tinctures as their basic medicinal preparations.
This is a good way to preserve the volatile essential oils of many plants, which are generally not soluble in water. For purists, an old method is to boil the ingredients in water until the desired properties are extracted. Strain the liquid, add the decoction to olive or other vegetable oil, and simmer until the water has completely evaporated. Add beeswax as needed to get a firm consistency. Melt the mixture by heating slowly, and stir until completely blended.