There are many things that people don’t necessarily “need” as far as self-sufficiency goes. Soap is not one of them. Knowing how to make soap from scratch with hardwood ash lye and fat might mean the difference between your family’s health and some terrible food poisoning or infected wounds.
This isn’t a complicated process, but it is a time-consuming one. Fortunately, making a big batch of soap in one go will generally provide enough to last several months. If you make extra, you can trade it with your neighbors.
The Basics: Lye and Fat
The most basic soap you can make from scratch is with simple lye from wood ash and some kind of fat.
If you want to get all fancy, you can add some herbs or essential oils into the mix later on, or experiment with different herbs and flowers infused in the fat you’ll be using.
But for now, we’re just making basic farmhouse soap.
Choosing a Fat
As mentioned in the ingredients section, you can use pretty much any fat or oil to make your soap from scratch. Really fancy ones will use a mix of things like olive oil, apricot kernel, coconut oil, etc.
For the sake of homestead soap, we’ll assume we’re working with things like leftover bacon grease, beef tallow drippings, and whatever’s lurking in the bottoms of your cooking oil containers.
If you’re using these drippings, it’s a good idea to heat them up and strain them through cheesecloth before making soap. Sure, you might not be bothered by coming across a chunk of bacon or beef tendon when you’re showering, but guests might find it a bit off-putting.
As far as ratios go, a basic soap like this will use a 1:3 ratio of oil to lye. Or, as folk wisdom calls it, “about two pounds of grease to a gallon of lye”. 
Of course, these are just rough estimates for creating a basic, all-purpose soap. If you want to get really precise, then be sure to look up fat-to-lye ratio tables for all the different fats you could use.
I highly recommend doing as much of this soapmaking process outside as possible. Lye gives off really toxic fumes, so fresh air is your friend. Also remember that this stuff can be dangerous. Doing this process outside, away from small children and pets, is really the best option.
All About Lye
If you’ve never worked with lye before, you may be wondering what it is. In simplest terms, it’s an extremely alkaline substance that’s been used as a cleaning agent for thousands of years.
The powdered form you can buy at the store is generally sodium hydroxide. The stuff we’ll be making from ashes is potassium hydroxide, or potash.
To make your own lye for homemade soap from scratch, you’ll need to collect ashes from burnt hardwood. If you’re not familiar with that term, hardwood trees are generally deciduous, with dense wood.
Oak, maple, beech, hickory, and ash are the best woods to burn to make soap. In contrast, softwoods are generally coniferous, like pine, spruce, and fir. These have too much resin in them to mix with fat.
If you want to know more about the history of lye and how to use it safely, we have a whole guide that you should check out.
Supplies You’ll Need
- Hardwood ashes
- Leaching barrel (instructions below)
- Fat(s) such as tallow (beef fat), lard (pork fat, like bacon grease), olive oil, etc.
- A large stainless steel or glass pot (do NOT use aluminum: the lye will burn right through it)
- Plastic or wooden spoon, spatula, etc.
- Scales to measure weights
- Mold to pour the soap into (a wooden or silicone mold is ideal, but you can use small cardboard boxes or even old Pringles cans)
- Protective equipment such as long-sleeved shirts, gloves, safety glasses, breathable face mask, even a full-face plastic protective face covering.
- White vinegar: lye is extremely caustic, and can cause severe burns. Have white vinegar on hand to neutralize it just in case it splashes.
How to Make Lye
Sweep out your wood stove or fireplace thoroughly before starting to make your soap from scratch. This is to make sure that you’ve gotten rid of any softwood ash from previous fires.
Then burn enough to fill a large box with ashes.
Assemble Your Leaching Barrel
Next, you’ll want to create a leaching barrel. When you create this, you can pretend that you’re a medieval peasant about to do your annual laundry.
You see, before people figured out how to make soap, they would create basic lye solutions, run that through their clothes in this kind of leaching barrel, and then rinse them.
The lye would react with the body oils that had accumulated in their clothing and adhere to any dirt particles within the fabric’s weave. Then the water they rinsed through everything would wash all that grime away.
Since most clothes were made of either wool or linen (which shrinks in hot water), this was a really effective process. But I digress.
To make your leaching barrel, get a large wooden container and drill several 1/2 inch holes in the bottom. If you can’t get hold of an old wooden barrel or similar, a steel drum would work too. It’ll just be harder to punch holes in the bottom.
Prep the Ash
Place your barrel onto cinder blocks so it’s a few feet off the ground. Then create an angled trough to go under the container to direct the liquid into another steel or wooden container.
Add in about an inch of pebbles or gravel, and then lay 4-6 inches of straw on top of that. Then shovel those hardwood ashes atop the straw, filling the container as high as possible.
Be sure to tamp these down layer by layer, so they’re fairly compressed. Once you’ve filled the container, create a depression in the top ash layer.
Now, add your rainwater. A container of water that’s about 1/3 the size of your leaching container should do the trick.
Check back after about 12 hours, and you should find a significant amount of liquid in the catchment container. This will be strong enough to wash basic oil or grease away, but you want a very strong solution.
Repeat this process with more ashes; only this time, pour the strained and collected solution through the barrel instead of fresh rainwater. Keep doing this until the strained lye is strong enough to float a fresh egg in it.
The egg should float at the halfway point. If it floats too high, you need to add a bit of water. If it sinks too much, you’ll need to run it through more ashes. Don’t eat the tester egg, as it’ll be really toxic.
Combine the Lye and Fat
Now it’s time to move onto the next step of making your soap from scratch.
When it comes to mixing the fat and the lye, try to make sure that these ingredients are the same temperature. This is important for the right chemical reaction to occur.
Fats usually need to be heated to about 100°F in order to melt them properly. This is especially true for animal fats like lard and tallow. Try to have two burners going at the same time so you can heat up the lye to between 95°F and 100°F.
Next, you’re going to add the lye solution to the fat. As you can imagine, this requires you to heat up the fat in a much larger pot than the lye, to accommodate both amounts.
At this point, the Appalachian folk method (which is mentioned in the first Foxfire book, if you’re so inclined), is to stir it regularly for a good 20 minutes.
What you’re looking for is something called a “trace”. That soap mixture will look a bit like cottage cheese when you first combine it. It’ll thicken up and go creamier as you keep blending with your spoon or stir stick.
This is the point where you can add some essential oils, if so inclined.
Pour the Mix Into a Mold
After that 20 minutes or so, pull the spoon out and drizzle a bit of the mixture across the surface. If it leaves a sort of trail across the top, then that’s the “trace.” This means that the mix is ready to pour into your molds.
However, if it sinks, you need to stir it a bit more. If it sits right on top like custard, pour it into the molds immediately. Otherwise, you’ll have a solid pot of soap, and nobody wants to have to carve that up.
As mentioned, your molds can be pretty much anything that’ll hold the mixture in a fairly solid shape for a while. We use old bread baking tins that we’ve found at thrift shops for a few pennies.
If you’re worried that the soap won’t release from the molds easily, line them with waxed paper first. Of course, if you’re using a metal mold, you can just heat the sides when you’re ready to take the soap out, and that’ll melt the edges enough, so it just pops out.
Let this soap sit in the mold for at least four to six weeks before you even think about cutting it and using it. The soap is still quite caustic at this point.
You can use it if you absolutely have to, but you might end up with a bit of a rash. It’s best to allow it to cure for a good six months, if possible. Then, use a piece of wire to cut it into slices.
You can use these soap slices for pretty much anything. I’ve grated them to use as laundry or dish detergent and used them whole for washing my hands.
Feel Free to Get Creative
Remember that you can add all kinds of different things into that basic soap from scratch mixture.
For example, if you do a lot of work in the garden, exfoliants are good. You can stir used coffee grounds into a small batch to wash your hands with, and that’ll scrub grime off really well.
Once you know the basics, you can adapt this recipe to pretty much anything.
Best of all, you’re ensuring that nothing on the homestead goes to waste. That honors every aspect of rural life, with nothing ever taken for granted.