How to Make Lye From Scratch Using Wood Ashes and Water

Only If You Absolutely Have To

handmade white soap
chizu / Getty Images

Few developments in the history of making soap have made quite the difference to the industry and craft that the development of laboratory-made lye has made. While it has been more difficult to procure in recent years, it is still widely available to soap makers.

But lye wasn't made in large-scale labs until the mid-1800s and has been available to the home-based soap maker only the past few decades. Soap has been around for thousands of years. What did people do before that?

They made their lye the old fashioned way by leaching water through wood ashes layered in a barrel or other container. If you're in a far corner of the globe and can't get lye locally, or are just curious how it's done, here are sources of information that can show you.

  • 01 of 08

    The Basics of Making Lye

    Lye is potassium hydroxide, sometimes called caustic soda. It has a pH of about 13 and this level of alkalinity can burn your skin and corrode some materials. To make lye with rainwater and hardwood ash, you need a wooden barrel and safe containers to capture the leached lye water. You will need safety goggles, rubber gloves, and boots to handle the lye water safely.

    • Collect ash from hardwood fires (such as ash, hickory, or beech). Softwoods do not contain enough potassium. You need soft water that has few minerals, which makes rainwater a good source if your local water is hard.
    • Drill holes near the center of the bottom of a wooden barrel. Place a layer of clean pebbles and then a layer of straw in the bottom of the barrel, which will act as a filter.
    • Prop the barrel up on blocks or a frame and position a lye-safe bucket underneath the holes in the bottom. Stainless steel and heavy-duty plastics are often lye-safe, but aluminum is not.
    • Fill the barrel with wood ash to within 4 inches of the top. Slowly pour rainwater over the ash. Note how much water you add so you know how much lye water will be produced. You will need enough lye-safe buckets to match the amount of water you add to the barrel.
    • Collect the lye water until it is within 4 inches of the top of the bucket, then replace that bucket with another lye-safe bucket. Use safety gloves, goggles, and boots when handling the lye water.
    • Test the pH of each bucket of lye water to see if it is 13 or more. Carefully pour the bucket of lye water back into the barrel if it is below 13 and collect it again. Repeat this until your buckets of lye water are pH 13.
  • 02 of 08

    Wikihow—How to Make Lye

    This article that makes it sound so easy until you realize how much equipment and ingredients you need and how involved the process is. But the instructions are very clear and easy to follow.

  • 03 of 08

    Where to Buy Lye

    The science and history of making lye may be interesting, but there are affordable ways to buy lye. You may want to take the easy route to get lye that is reliable and accurate.

  • 04 of 08

    Mother Earth News—Soap Making in the Bush

    Published in 1972 (the same year Ann Bramson's "SOAP" was published), this fascinating article shows how the author learned "to survive on less than $10 a month cash money by trapping, tanning, foraging food and dipping candles from our own tallow and lard" and "quickly mastered the fine and easy art of recycling hardwood ashes and left-over kitchen fats into clean, all-purpose soap." It almost makes you want to go out into the wilderness and try it. 

    Continue to 5 of 8 below.
  • 05 of 08

    Making Lye from Scratch Video

    This YouTube video shows a woman (wearing appropriate pioneer garb) and her lye-making box. It is useful to actually see the setup rather than just a diagram. The audio is terrible, but the information is great.

  • 06 of 08

    End Times Report—Making Lye Water

    This article describes an interesting technique using modern items like buckets and plastic spouts to make an "automatic lye machine." It includes an interesting variation using a rain gutter and spout. It says that lye made from kelp (seaweed) ashes make the hardest soap.

  • 07 of 08

    Lye From Wood Ash

    This article gives yet another perspective, this time, from a biodiesel frame of reference. Folks making their own biodiesel are using a process very similar to making soap.

  • 08 of 08

    Rogue Turtle's Guide To Soap Making

    If in addition to information about survivalism, camping, food storage, cooking, and self-reliance, you need to know how to make soap.