Wood Ash mixed with water produces lye, which can then be mixed with animal fat to make soap. You simply have to add boiling soft water to your ash, allow it to sit for a few days, and drain the lye out of the mixture. You know that it’s alkaline enough to go forward with the soap-making process when an egg will float in it. Once you’ve extracted the lye, it’s just a matter of cooking it down with rendered animal fat. Softwood ash produces a soft soap and hardwood ash produces a firmer soap. Add salt to make it even firmer.

A cord of wood can produce up to 50 pounds of ash so if you burn wood all winter and spring, you’re going to have plenty of ash at your disposal!

 Taken from https://www.survivopedia.com/survival-uses-of-wood-ash/