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Wood Ash

This experiment comes from an article I read on technological developments. While reading about ways to make iron, glass, and other historic processes, I became fascinated about the section on soap making. Now, we will not go through the entire process of making soap (at least not this week), but we will experiment with the first steps in classic soap making.

To do that, you will need:

  • a sheet of writing or typing paper
  • a butane lighter
  • aluminum foil
  • two disposable cups
  • isopropyl alcohol (rubbing alcohol)
  • turmeric spice

In classic soap making, done the way it was two hundred years ago, you need some potassium hydroxide, which will be combined with fat to produce the soap. Luckily, potassium hydroxide can be recovered from a substance which was very common for pioneer families. Wood ash. The ashes left behind from burning plant material contain calcium carbonate, potassium hydroxide, and sodium hydroxide. Different plants produce different quantities of each, and hardwood ash is the best for potassium hydroxide.

Instead of building a hardwood fire, we will burn some paper. Think about it. What is paper made of? Wood. So burning the paper will leave behind ash that contains the potassium hydroxide that we want.

Now, don't rush to start burning the paper. First, tear off about an inch of one corner and set it aside for later. Also, we don't want to accidentally burn anything besides the paper. To be safe, place a sheet of aluminum foil in the bottom of your sink. Then crumple a sheet of paper into a loose ball, and place it in the center of the foil. Warn any other people in the area that you are going to burn the paper, because the smell of something burning can alarm people if they are not expecting it. That can wind up with you getting in trouble, which is a bad thing.

Once everyone is warned, use the butane lighter to set the paper on fire. Wait for the flame to burn down. The paper will turn black, and then at the edges, it will start to turn white. That white is what we want, so we will help it along a bit. Use the butane lighter to heat the black areas a bit, so they will burn completely, giving you more of the white ash. You don't need all the black to turn white, so don't use up your lighter. Once about 1/4 of the remains are light grey or white, let the rest of the fire go out, and wait for the foil to cool. Then pour the ash into one of the disposable cups. Add about a teaspoon of water, and swirl the water around to mix it well. Set this aside. Keep the foil, as we will need it later too.

In the other disposable cup, put about a tablespoon of rubbing alcohol. Then add about 1/8 teaspoon of turmeric. Turmeric is a spice that you can find at the grocery. Be careful with the turmeric, as it will stain clothing, skin, and just about anything else (which is why we are using disposable cups.)

If you have watched the Making Turmeric Paper video you will remember that turmeric acts as an indicator, turning red in the presence of a base. Potassium hydroxide is a strong base, so if our ash contains potassium hydroxide, then it should cause the turmeric to change colors. To test that, pour a couple of drops of the ash/water mixture onto the foil. Then add a couple of drops of the turmeric/alcohol mix. Watch as the two mix. It should turn a deep red, indicating that the ash/water mix is a strong base.

But wait a minute. Maybe the paper was basic to start with. That is why we tore the corner off the paper. Place that corner onto the foil and add a couple of drops of the turmeric solution. It colors the paper yellow, not red, showing that the base was produced when the paper burned.

If we were going to make soap, we would need a LOT of ash. Then we would filter water through it to remove the potassium hydroxide. That water would be collected and boiled to concentrate it. Once we had a very concentrated solution, it would be mixed with rendered fat, forming soap. That is a long, messy, smelly process, so we will stop here for now. Instead, I will work on another mixture, involving ice cream and chocolate syrup, which usually leads to the need for some soap.

Have a wonder-filled week.