If you’ve ever made soap, you may be wondering, “Can I make soap more sustainably?”. Well, I have exactly the solution for you! You can make lye from wood ashes to make your own sustainable soap.

At its very basic form, soap is made from lye and fat. For the fat, you can use oil, tallow, or milk. I’ve never made it before, but that IS one of the things I’m going to try this year. It will be a future episode of my Self Reliant Skill of the Week.

Most soap makers buy lye to make their soap. But that’s not very sustainable, is it? If you’re shooting for self reliance and sustainability, you really should consider making your own lye. It’s a fairly easy process, one that pretty much anyone can do.

It's easy to make lye from wood ashes

What is lye?

Lye is a natural but very alkaline chemical known as sodium hydroxide. Lye is used in soap, to make biodiesel, to cure foods, to unclog drains, and to disinfect toilets and floors. The most common use for lye is for making soap. In fact, according to the FDA, soap has to be made of sodium hydroxide to be called soap.

When you’re working with lye, it’s best if you can do so outside, and keep the kids away from it. If you have to work with it inside, make sure it’s in a very well-ventilated area, and wear a mask so you don’t breathe the fumes. Lye can cause real damage to your lungs if you breathe it in.

Lye is very caustic, so you should wear eye and hand protection when you’re handling it. Safety glasses and rubber gloves are a good idea. Lye is extremely alkaline, so it can cause burns. Please handle with care!

Use your homemade lye to make homemade soap

Supplies needed to make lye from wood ash

To make lye from wood ashes, you just need a few basic supplies:

  • hardwood ashes.
  • 2 plastic 5-gallon buckets
  • small amount of gravel, sand, and straw
  • soft water (rain water, distilled water, or well water)
  • 1 raw, uncooked egg
  • cast iron, ceramic, or steel pot
  • outdoor burner
  • milk jugs for storage
  • safety glasses and/or rubber gloves

It’s very important that you use ashes from hardwood trees, as hardwood ash has the proper amount of potassium needed to make soap. The potassium from the hardwood trees actually stays in the ashes after the wood is burned, so it can easily be leached out with the addition of the water. Hardwoods include alder, maple, hickory, oak, and walnut.

Don’t use ashes from pine, redwood, or spruce, as these are softwoods that don’t retain the proper potassium levels after burning. I burned some Russian Olive specifically for this project, as we usually use pine or Douglas Fir in our wood stove.

I know, the egg seems like a funny thing to use for making lye, but it’s to check the concentration of the lye. You’ll understand in the next section!

Interestingly enough, lye can actually eat through aluminum, but not plastic. So make sure you use a stronger metal if you need to boil your lye. Cast iron, ceramic, or steel are good choices for pots. And you will want to store the lye in plastic jugs until you are ready to use it.

The process of making lye from wood ashes

This is how I made lye from wood ashes as a complete beginner.

  1. Put a nail toward the bottom of a 5-gallon bucket, and leave the nail in it. Put a layer of rocks, a layer of sand, and a layer of straw in the bottom of the bucket. This will act as a filter. Then fill the bucket as much as you can of the hardwood ashes.
  2. Set your bucket into a second bucket, to catch any leakage that may occur through the nail hole. Fill the bucket with soft water (rain water is best, but well water will work too). Let the ashes and water soak together for 12-24 hours.
  3. After the soaking time, raise the inner bucket (the one with the ash/water mixture) up above the outer bucket, and sit the bucket on 2 2X4’s placed on the upper rim of the outer bucket. Pull the nail out of the hole and allow the water to drain. Be very careful handling this lye water, as it is very alkaline and can cause burns.
  4. Once the water has drained out of the ashes, you will need to check the concentration of the lye. Do this by gently putting an egg in the lye water. The egg will float if the lye is concentrated enough. If it sinks, you will need to boil the solution to remove some of the water from the lye.
  5. If you have determined that you need to boil the solution, use a cast iron, ceramic, or steel pot. Do this outside if at all possible. Bring the solution to a low boil, and allow to boil until some of the liquid is reduced. Pour some of the solution into a smaller container and try to float an egg in it again. If it still doesn’t float, boil for longer. Keep doing this until you have evaporated enough of the water out of the lye, and the egg floats in your solution.
  6. When your lye is concentrated enough, store it in a glass or plastic container with a lid until you are ready to use it to make soap. Always store it in a safe location where pets and kids can’t get to it. Lye is so alkaline, it will cause serious damage if someone or something was to drink it.

This process is harder to explain in words than it is to show, so here is my video on making lye from wood ashes.

As you saw in the video, I may have boiled it too long or at too high of a temperature. I’m hoping I didn’t screw it up!

Are you going to try to make your own lye?

Well, are you going to try it? Or have you ever tried it? Did I mess up on my first try? Please let us know your experiences with it in the comments. Let’s learn together!



  1. a question, i have made soap before, bars and liquid. how do you measure this liquid lye for a recipe where i would normally use lye crystals? do you just go by weight still?

    1. Yes you just go by weight still, but don’t dilute it. So you should be able to use this lye water in place of what the recipe calls for, for the crystals and water combination.

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