Soapwort, also known as bouncing Betty or wild sweet William, is an herbaceous perennial plant native to Southern and Central Europe that provides an alternative to soap in shampoo making. People have used the plant as a cleanser for centuries, as it contains a mildly lathering substance known as saponin. When the plant's dried roots are simmered in water, the saponin is released, creating a gentle foaming effect. Available from bulk herb suppliers and well-stocked health food stores, soapwort often comes dried in 10- to 12-inch pieces, which are suitable for making shampoo.
Chop the dried soapwort root into 1- to 2-inch pieces with a sharp kitchen knife.
Place the dried soapwort root pieces in the saucepan, and cover with spring or distilled water. Bring the mixture to a boil over medium heat, then cover and simmer for 20 to 25 minutes.
Remove the saucepan from the heat, and add the dried herbs to the liquid. Place the lid back on the pan, and set aside to cool completely, which usually takes about 30 minutes.
Add the essential oil to the shampoo if desired, and stir well to combine. Choose essential oils that best complement your hair type.
Strain the soapwort shampoo mixture through a fine mesh strainer into the plastic storage bottle. Secure the lid on the bottle, and label with the contents, using a permanent marker.
Store the shampoo in a cool, dark place near the shower. Use within a week, or discard any leftovers and make a fresh batch. Shake well before each use, and use 3 to 4 tbsp. at each application to clean the hair and scalp.