Wood ash soap is a very cheap way to produce soap, but it does not always produce the same quality soap every time. Sometimes the soap is firm and sometimes it stays soft. Different ashes produce different lye solutions. If a more standard quality bar soap is wanted, or a bar soap that is of a good quality to sell, then making lye water using purchased sodium hydroxide is a much better. We ordered sodium hydroxide crystals from Kampala, the capitol city of Uganda about 10 hours away. I had access to a saponification chart for different oils and easily developed the recipe of sodium hydroxide to palm oil.
During the soap making program it was brought to my attention that the local women do not have measuring cups or scales in their households. I measured out the correct weight of the ingredients (sodium hydroxide, water and palm oil) and we poured them into empty plastic water bottles. They counted the ridges on the edges of the bottles to be able to duplicate the volumes of the ingredients to make the soap again.