Updated: Nov 23, 2018
How to make lye
Soap making in the woods can be almost automatic. Hardwood ashes are some of the best producers of lye. Add a bucket of rain water and some left-over cooking oil and you can easily brew up enough soap to clean everybody and everything.
To make concentrated lye water you need to pour rainwater through cold ashes, hardwoods are the best. You will need a barrel or clay flowerpot with a hole at the bottom. Layer the bucket with gravel and straw to keep the ashes from falling straight through. This will help form a filter medium at the bottom of the bucket. Tightly pack your ashes on top of the straw. Make sure to leave a few inches at the top to hold the water.
Next you need to set your bucket up so that the water can drip down through the ashes, out the hole in the bottom and into your stainless steel pot below.
Heat the lye water
If you have rainwater, heat it to boiling. You can use steam distilled water, but regular tap water has too much chlorine and minerals in it. Pour 1.5 litre of the boiling water over the ashes. Once that has seeped down, pour another 1.5 litre and wait 30 minutes before pouring another 1.5 litre into your bucket. Continue this step until you see brown lye water in your pot.
You are done pouring as soon as you have around 3 litres of brown lye water in the pot below your ash bucket. The used ashes should be discarded, you can put them in a compost bin to break down. If you need more lye water, repeat the process with fresh water and ashes. Ten cups of ashes and 3 litres of rainwater will make an average strength lye, so there’s no need to test the strength. The finished soap will vary a little in strength, but you can use slightly stronger soap for laundry, and slightly weaker as a bath soap if it varies too much.
Concentrate the lye
After extracting the brown lye water the next step is to boil it until the lye is more concentrated. When starting with ten cups of ashes, you should boil the brown lye water until you have just 3/8ths of a cup concentrated lye water. This should take three to four hours. Once you get down to about a quart of concentrated lye water in the pot you should watch it carefully so as to not boil off all your water. If you do go below 3/8ths of a cup, carefully add enough rain water to bring it to 3/8ths. Be very, very careful with the lye! Wear gloves, and be super careful not to splash or spill!
If the above method is too much of a hassle, book our Cold Process Soap DIY Workshop where you can buy lye from us and rent our facilities to make your own soap at our studio. If you are new to DIY soap making, no worries, join our Basic Cold Process Soap Making Class and learn the essential knowledge of making your own soap from scratch.
Today, DIY soap makers are using sodium hydroxide and potassium hydroxide (both are called lye as well) to make bar soap and liquid soap, respectively. These two materials are used for the reasons of convenience and accuracy of lye concentration. The second reason determines the success rate of soap making because different oil requires different amount of lye to turn into soap completely. You can learn the calculation of lye for successful soap making in our Advanced Cold Process Soap Making Class.