Pure Castile Soap Recipe

Grind ¼ cup dried or mince ½ cup fresh herb of your choice
(The soap shown was made with sage and oatmeal)
1 quart olive oil 
1 quart water
¾ cup additional cold water for diluting the lye 6 Oz. lye (also called “caustic soda,” chemically it’s sodium hydroxide, NaOH)**
Place the olive oil and the quart of water in a large nonreactive bowl (ceramic, glass, or plastic).  In a separate non reactive bowl,  carefully add the lye to the additional ¾ cup cold water — it will bubble and steam, and the lye can burn, so do this carefully.
Then add the lye solution to the olive oil and water base, stirring in a bit at a time, and again using great care. 
Stir the mixture with a long plastic spoon, mixing always in the same direction, until it thickens to the consistency of a thick bechamel — this can take some time, or you can whisk with a metal egg beater or a stick beater. 
Pour into glass or silicon pans (or an official soap mold) and leave to set for at least 24 hours. 
Turn out the soap, slice it into bars, and wrap in parchment paper to cure for another three to four weeks before using.
It will weep water while it’s curing, so you will need to re-wrap each bar before you store it for later use or if you want to give it as gifts.