How to Make Lye from Wood Ash

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Largely forgotten by the modern world, lye is still important to those interested in self sufficiency. Historically, lye has been used to make many foods like hominy, lutefisk, German pretzels, and Chinese noodles. Animal fats or vegetable oils are combined with lye to make homemade soap. Lye can also be used to chemically pulp plant matter for making paper. The modern world wouldn’t be the same without lye either; oven cleaner, drain opener, and biodiesel production all use lye.

Lye is a powerful base (alkali) that can be created using rain water and wood ashes. Lye created from wood ash is potassium hydroxide (KOH) whereas commercial lye is composed of sodium hydroxide (NaOH). Modern chemical engineering has all but replaced the traditional method of producing lye. For many homestead applications the difference in chemical formulae are inconsequential, but there are exceptions.

You only need two ingredients to make lye: wood ash and water. Collect rainwater -- it should be free of chemicals and excessive mineral levels that are found in city and well water. Using wood ash from broad-leaved hardwood trees will result in better quality lye than if you use ash from soft woods or conifers. Before discussing how to make lye, it is important to note that lye is very dangerous and extreme caution should be used when making or handling lye -- whether commercial or homemade.

Lye should never come in contact with aluminum as it will react with the metal. Lye can cause chemical burns if it comes in contact with skin, and blindness if it gets in your eyes. In fact, when you get lye on your skin, it will begin reacting with the fatty acids on your skin and begin making soap. Always make and use lye in a well-ventilated area, and keep pets and children at a safe distance. Pants, a long sleeved shirt, rubber gloves, and eye protection should be worn when making or using lye. If you get lye on your skin, use vinegar to neutralize the solution. Immediately call 911 or the poison control center if an emergency arises while working with lye.

There are numerous ways to make lye from wood ash. Some instructions suggest that you mix ash with hot water and let it set before filtering out the ash. Others will tell you to drill holes in the bottom of a barrel, cover with straw, and then fill with ash. Water is poured over the ash and lye is leached as the water filters thru the barrel and is collected by a pan underneath the barrel. This works, but your lye is likely to be discolored by the straw. When lye reacts with lignin in the straw, the bonds are broken down and the fibers are left behind. After enough leachings, the remaining straw fibers work as an effective filter, but will no longer discolor the lye.

Regardless of the method used, the more times you run the lye solution through a bed of ashes, the stronger the lye will become. Instead of successive leachings, you can also boil the lye to strengthen it. The water will evaporate but the lye will not, so the solution will contain a higher percentage of lye.

One of the difficulties when making lye is determining proper strength. One traditional method of determining strength is to see if a chicken feather will start to dissolve when placed in the lye water. A more accurate measure is to float an egg (still in the shell) in the lye solution. If the lye is of proper strength, the egg will float but only a quarter sized circle of the egg will be raised out of the water. If it floats too high, the lye is too strong. If it doesn’t float high enough, then the lye is too weak. Discard the egg after testing; it is not safe to eat.
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The ease of manufacturing and the wide variety of uses makes lye production a skill every homesteader should learn. We do not recommend that lye be used for food production due to the inherent risks, and extreme caution should be exercised at all times when working with lye. When used with proper care, however, lye is a powerful tool to reduce your dependence on the outside world.