how to make lye from wood ash

This past school year our family took a deep dive into pioneer life. One fictional pioneer account that we read referred to the making of soap with lye made from wood ash and rain water. We thought “We have wood ash. We have rain water. We can make lye!” And so we did. And that’s no lie. (Sorry, I can’t help the mom jokes.)

This activity was interesting because of our pioneer study, but also because I could teach my kids the science behind pH. We looked at the pH scale, and talked about what the various numbers on the scale represented. In order to make true lye, the pH has to be 13. This is the same alkalinity as bleach, which goes to show how strong, and potentially dangerous, lye can be.

To make lye from wood ash you will need:

• wood ash (duh)- We had about 2 gallons of ash.
• rain water- Don’t forget to leave buckets out to collect this!
• medium size rocks (not pebbles or the spout will clog)
• hay or straw- Dry out some lawn clippings if it’s all you have.
• 5 gallon plastic bucket or wooden barrel with a spout; do not use metal- We used a bucket for collecting honey.
• a plastic bucket or sturdy glass container to collect the lye; do not use metal
• pH strips
• disposable gloves and some sort of eye protection

To make the lye:

First, place the bucket high enough that you can drain it from the spout without having to move it. We placed our bucket on cement blocks. I highly recommend that this entire process be done outdoors and in a place where the bucket will not be bumped or knocked over.

Then, place a layer of medium size rocks on the bottom of the bucket (or barrel). These are to keep the straw and ash layer from clogging the spout.

Next, place down a nice thick layer of straw or hay. We used a couple good handfuls.

Then, pour in the wood ash. Do this carefully so you don’t create a cloud of dust!

After that, you can pour in the rain water if you have already collected it. We had to wait for the next rain before we had enough rain water to add to the bucket. Thankfully, we live in the Pacific Northwest, so we soon had about a half gallon of rain water. After the water is in, put the lid on the bucket.

Then, you wait. We removed the lid every few days (when we remembered!) and checked the level of the water. It filtered through the ash slowly. After a couple of weeks, there was no water sitting atop the wood ash, so we decided to drain it.

Wearing gloves and eye protection, I placed a half gallon mason jar under the spout and opened it up. We were shocked at how dark the liquid was, and even more shocked when we checked the pH strip- we had done it!

If your lye is not alkaline enough, simply pour it back in the top of the bucket and let it filter through again. Chances are that it will come through at the correct pH the next time.

Have you made anything with lye? Any suggestions for what we should do with it? Please leave ideas in the comments below!

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