WARNING: Lye is highly caustic and will degrade organic tissue. Do not allow lye to touch your skin, breathe in the fumes or be taken internally in any way. It will cause chemical burns, permanent scarring or blindness. Do not ever combine lye with aluminum, magnesium, zinc, tin, chromium, brass or bronze. When using or making lye, always wear protective equipment including safety glasses and chemical resistant gloves, and have adequate ventilation.
Basic homemade lye soap is useful for so much more than cleaning up the language of wayward children. Grandma used to rub it on dirty stains before washing. It is very soothing to sensitive skin, since the glycerin contained in homemade soap helps to clear acne, eczema and psoriasis. It eliminates the “human scent” on hunters. When rubbed on a poison oak, ivy or sumac reaction it will cool the itching when allowed to dry. Grandma used to tie a bar in an old sock and hang it on the porch as a bug repellent, and spread the scrapings around the base of the house to repel ants, termites, snakes, spiders and roaches. It was often used as a lubricant on machinery, drawers, and hinges.
Soap was discovered in Ancient Babylon as early as 2800 BC. It is thought to have been made for the first time when grease from the cooking pot boiled over and combined with the ashes from the camp fire. Our forefathers picked up the resulting soap and found that it was a good tool to keep themselves clean. Modern soap was made in regular practice as early as 300 AD in Germany .
The Saponification process
In its simplest form, soap is made from oil or fat, water and lye. Now, we buy concentrated lye and dissolve it in water before combining it with oil, but before modern lye could be bought at the store, people would take the hardwood ashes from their cookstove, store it in an old carved out tree or wooden barrel, and then pour rainwater through it to make the lye. They would test the strength of the lye by floating an egg in it. Then they would pour the lye into the warmed fat and stir it. When the fat and lye are combined, a chemical reaction takes place. There is no lye or fat left—they are combined to make something called soap.
Store bought lye is known as Sodium Hydroxide since it has more salt than does homemade lye, which is called Potassium Hydroxide. Sodium Hydroxide makes a much harder soap than Potassium Hydroxide. To make a harder soap out of homemade lye, add ½ tsp. of table salt for each pound of fat.
Tallow (beef fat), lard (pork fat) or vegetable oils can be used as the base for soap. These fats are called triglycerides. When the triglyceride is treated with lye, it rapidly forms the ester bond and releases glycerol (glycerin), the natural byproduct of saponification. Most homemade soap contains glycerin, which is why it’s so good for the skin; many commercial operations remove it for other applications.
Making the Lye
Lye making requires hardwood ash. Hardwoods include any fruit or nut trees and any of the following: Alder, Apple, Ash, Aspen , Beech, Birch, Cherry, Cottonwood, Dogwood, Elm, Gum, Hickory , Locust, Maple, Oak, Olive, Pear, Poplar, Rosewood, Walnut, or Willow . Softwoods are to be avoided for this function: Cedar, Spruce, Pine, Fir, Hemlock, or Cypress .
In a wooden barrel or hollow tree, drill some holes in the very bottom, then set it up on a stand to allow room below for a pot to catch the lye water. Some people make a barrel with a removable plug which they remove after letting the water sit in the ash. Under the stand, set a wooden or glass pot to catch the drip.
In the barrel, put first a layer of gravel, then a layer of straw or dried grass. Fill up the barrel with hardwood ash. When you are ready to make the lye, pour rainwater or other soft water through the ash. The minerals in hard water will interfere with the chemical reaction between the lye and the fat. The water may take up to a few days to drain through. The spent ashes can be composted or added to the garden.
In a specified purpose soap-making pot such as cast iron, boil the lye until a fresh, in-shell egg will float on top, with about half of the egg still above the surface of the lye. If it’s too high, add more water, if it won’t float, it needs to cook down a lot more or else be poured through a new batch of ashes. The egg will need to be destroyed after use. Another test of the lye strength is to dip a bird feather in it, and if it dissolves, the lye is strong enough. Don’t test it with your finger; if it’s strong enough, it will eat off the skin.
Rendering The Fat
After the animal (beef or pork) is butchered, take the fat and skin that you set aside and fill a heavy bottomed pot. Pork is the preferred fat for soapmaking. It’s best to render it outside so as to not stink up the house. We have used a homemade propane burner on legs, with a funnel to channel the air to make the flame hotter. Something similar could be made to use with wood heat. Simmer the fat in the pot, then ladle the liquid fat out of the cooking pot. We killed a 400 lb. hog and got about 10 gallons of rendered fat.
Making Soap—The Cold Process
If using commercially produced lye, it’s possible to use a cold process, where you warm the fat and dissolve the lye in water, then add the lye water to the fat and put in a blender and mix it, then pour into a mold. The emulsification starts when it “traces” with a spoon dragged over the rippled mixture. It has to set for 6 weeks in the mold to be properly mixed.
1 lb. Commercial Lye soap recipe
¼ c. commercially produced lye
¾ c. soft water
2 c. (1 lb.) fat
6 lb. Commercial Lye soap recipe
13 oz commercially produced lye
1 ½ pt. soft water
12 c. (6 lb.) fat
Instructions: Suit up in safety goggles, gloves and long sleeves. Start with room temperature or cooler water. [Correction by JWR.] Add the lye to the water. This will warm the water substantially. Stir well, making sure you don’t breathe in the fumes. Set the mixture aside to cool, preferably outside or in a well ventilated area.
Melt all the oils together in a lye-tolerant pan. Allow them to cool to approximately 110°F or within 5° of the lye water.
Add the lye water to the melted oils, never the oil to the lye water. Stir vigorously until “trace” occurs. This can be done in a blender if you so desire. If you are stirring by hand, it may take an hour or more for it to trace.
Pour the traced soap mixture into your molds. Cover. Cut after 3-7 days. Allow to sit for a full 6 weeks to cure and finish the saponification process.
Making Soap—The Cooked Process
It isn’t recommended to use homemade lye with the cold process. The cooked-down lye water is added to the fat and then mixed as it cooks. The reactive time is shorter, since the mixing is done in the pot instead of setting in the mold. It still needs to set for four weeks or so to harden.
1 lb. Homemade Lye soap recipe
¾ c. lye water
½ tsp. salt
2 c. fat
6 lb. Homemade Lye soap recipe
4 ½ c. lye water
1 Tbsp. salt
12 c. (6 lb.) fat
The amount of lye will vary, depending on its strength. This is a starting measurement. The old timers would mix it up and see how well it set. If it was still watery, they’d add more lye and cook it some more. If it set up too hard, they’d add more water, because they didn’t want the soap to crack.
Mix the lye water, salt and fat in the pot. They need to be about the same temperature. The mixture is then heated and stirred until the emulsification (trace) happens. The heating and stirring enables adjustment of the amount of fat or lye, but nothing should be added until it is well heated. Pour into the mold. Cover. Cut after 3-7 days. Allow to harden 4-6 weeks.
Essential oils can be added to the fats before the lye is added. You can choose your own combination. The amount of essential oils needs to be part of the total amount of fat, so the soap isn’t made soft from too much oil. Botanicals, herbs, oatmeal, citrus peels, or any other desired additives can be added after the soap traces, and then it can be poured into the mold.
No metal should be used as a soap mold. It’s best to use a flexible material such as plastic, for ease of removal. I mostly search thrift stores for old plastic storage boxes. The old-timers made wooden molds with removable bottoms. Or you can line a glass mold with plastic wrap before pouring in the soap.
Once you’ve used homemade lye soap, you’ll never go back to the store bought stuff. It sounds like a lot of work, but it’s so much better than anything found on a store shelf.