Now lye soap can be made two ways and I will tell you about both ways. You can even make lye soap today! The way pioneers made their lye soap was to save their cook stove wood, ash wood, and place it in a "ash hopper", hang it outside and when it rained this would drain it and what was left was lye. Now before putting your ash ashes in the "ash hopper" you would strain them getting anything out that would harm the final soap. You have to drain the ash with the rainwater so your soap will be pretty and white when it is finished, this is also called leaching wood ashes. After the rainwater draining you need to strain the left over product one more time. When you have enough lye to make a batch of soap (this would be about the same amount as a box of Merrywar lye that you would buy in the store today), get the fire going under the kettle. You use old skins and fats to cook out about 5 pounds of grease, when it is all cooked out you strain the grease and throw away the skins and cooked out fat pieces. Put your lye and grease in the "wash kettle" and cook over the fire stirring with the same paddle that we rendered lard with in the hog killing. This soap when finished cooking will be snow white, now if you want it to smell pretty you add a few drops of your favorite good smelling perfume or herb such as rosemary, jasmine or which ever one is your favorite.
The more modern way to make lye soap is to buy a box of Merrywar Lye, the Merrywar was a brand name but the only brand I ever heard of. You use five pounds grease (regular bacon grease as long as it isn't burnt works fine) and a box of store bought Merrywar Lye in the "wash kettle" over a just right temperature fire and the finished product is lye soap. There again you can add a scent or leave it as is. Lye soap was used back yonder when to wash clothes in the "wash kettle" and it sure made them pretty and clean.