When you heat with wood, you get ashes…And when you have ashes, you can make old-fashioned soft soap!
Soap is as old as human history. As we define it today, soap is the product of a simple chemical reaction called saponification. In saponification, a fat reacts with an alkali to produce soap. The original alkali was lye produced by running water through ashes. That lye was combined with lard. Lard was rendered from animal fat, which was set aside when animals were slaughtered for household food.
This old-fashioned type of soap-making is probably most familiar to our generation (if it’s familiar at all) through the pages of Little House on the Prairie. Laura’s family made a soft brown soap for their daily use by combining fat rendered from butchering with lye made from wood ashes.
And we found ourselves, on our little homestead in Downeast Maine with a woodstove full of ashes, beginning to wonder…Could we make soft brown soap for our daily use, too?
Turns out, making soap from wood ash has been a great solution for our family. We get to use ashes that would otherwise just be a waste product. It’s fairly easy after you’ve worked through it once. And it produces a whole lot of soap that we now prefer to any other soaps we’ve ever used! It’s squeaky-clean without being drying, and we use it for hand-soap, shower-soap, face-soap, and even shampoo.
Soap-making supplies are simple, but it does take a little planning ahead and a little set-up.
For the fat portion, since we don’t have any animals to butcher, we use our standard soap base, which is a blend of olive oil and coconut oil. It produces a soap that is more gentle and moisture-rich than the original lard variety.
The next step, which takes a bit more work, is making lye from ashes.
Caution: Lye formed from wood ash is potassium hydroxide, a salt with an extremely low pH. You may hear it described as “extremely alkaline” or “extremely basic” or a “strong base.” Just like strong acids, it can be very harmful. Lye is caustic, which means that it can cause severe burns and irritation, and must be handled carefully. We don’t want to get it on our skin, and we don’t want to inhale the fumes while it’s boiling down, so we use an outdoor propane stove. Lye also corrodes metals and some plastics, and so all of our lye processing is done in stainless steel and HDPE containers.
The basic principle for making lye is to drip water through ashes. The water leaches salts from the ashes and produces lye. In order to make the best soap possible, you’d like to have clean, strong lye. So, the first year that we made lye, we learned a few things that made lye-dripping more efficient and successful.
First, we filter our ashes. Removing all of the partially-burned fragments and sifting down to fine ashes makes the dripping process much more thorough. Joe stretched hardware-cloth over a wooden frame to make a sifter that fits over a storage bin. Each morning, we clean out our woodstove into a small bin, and when it’s full, we carry it outside and sift it into the storage bin. We do this all winter until we stop using the woodstove, and then we have our supply of ashes for the year’s soap.
2: a drip system
We also set up a drip system, to make it easier to process multiple batches of lye. Joe drilled a hole in the bottom of an HDPE storage bin and installed a valve. We set the bin up on four logs, with a stainless steel bucket underneath to collect the lye.
Once all the supplies are collected and the drip system is set up, you’re ready to start processing.
Place a handful of straw in the bottom of the bin, covering the valve-drain. Cover the straw completely with sand.
Fill the bin approximately half-way full with sifted ashes. Fill the bin with water to about two inches above the top of the ashes. We use well-water. Open the valve to let the lye drip into the bucket.
At this point, having the drip system lets us work on other things while the water slowly seeps through the ashes.
Once the bucket is full, turn off the valve, and carefully transfer the lye from the bucket into a large stainless steel pot for the next step.
Repeat until you’ve emptied the bin. Discard the contents of the bin into a compost pile, then refill and repeat as many times as necessary to work through all of your ashes.
3: boiling down
Everything that we read said that the lye that dripped through the ashes should be strong enough to make soap. But it wasn’t.
We determined that we had to boil it down to increase the concentration to make it strong enough for soap.
This is not any kind of work that we wanted to do inside, so we purchased a two-burner outdoor propane stove. This stove is multi-use for us – we boil down lye for soap, and also maple syrup and sea salt.
To boil down the lye, we use a tall stainless steel pot and the lowest heat setting. As the water boils off and the lye thickens, it bubbles up, so we always make sure that we leave lots of headspace in the pot for each batch.
On this crisp fall day, the dark surface of the lye was a stunning mirror of the rippling golden leaves above…It was mesmerizing!
And as the lye was boiling down, I was also fascinated by the incredibly colorful bubbles that formed on its surface!
To know when the lye had reached the appropriate strength, we ultimately settled on the egg test. Although we tried pH strips, only the egg-test gave us an accurate result for lye that was actually strong enough to produce soap. The egg should float at least half-way above the surface of the lye when it is at the right strength. You can see in the first test that the egg is quite low, so we continued to boil it down. In the second test, the egg is very buoyant, and this lye was ready for soap.
ready for soap!
And now, it’s time for the chemical reaction that we’ve all been waiting for. All of this preparation, the ash-collection, the sifting, the dripping, the boiling down and testing, has all led up to this moment of truth, when oil is added to lye and becomes soap!
You can instantly see the beginnings of the chemical reaction as the color changes during mixing. And then it’s just a matter of stirring frequently until the batch thickens to an overall creamy consistency. Once it’s creamy, it’s ready to use, but it will also continue to cure over time.
During the curing process, the soap will continue to thicken. Any excess liquid can be drained off. One winter’s worth of ashes produced about 3 gallons of soft soap.
What better way to use up the aftermath of heating our home than to make soft soap, the old-fashioned way!
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by Sydney Michalski