Chapter IV
Jimmy's Class Makes Soap

          Jimmy took his chemical set to school next morning. Miss Dean had said that she would be glad to have one or two brought to school in case there was need for them.
          On a table in front of the schoolroom there were some interesting bottles and jars. The boys and girls were looking at them and wondering what they were when Jimmy entered.
          There was one bottle marked PALM OIL. The contents were red-orange in color. Another had a green liquid in it, and was labeled OLIVE OIL. Still another contained something as white as lard, but it was called COCONUT OIL. And there was a jar full of something looking very much like the fat on the top of cold lamb or beef gravy; and sure enough it was labeled HOUSEHOLD FAT. Near by stood a can with a printed label saying in big red letters. LYE, and giving the manufacturer’s name.
          Miss Dean stood by, smiling, and saying, “No, I won’t tell you yet what all this is for. You must wait until the industrial science period.”
          (Can you guess what these things were for?)
          During the morning Jimmy had a chance to tell the class about making soap in olden times, and how he helped do it two hundred years ago! Miss Dean gave part of the language period to the class to ask questions and talk over what Jimmy had told them.
          Everyone was interested in Jimmy’s account of how lye was made in olden days, of how the fat was melted in the big kettle and the lye poured in, and of how the kettle was then boiled and stirred until the lye combined with the fat to make soap. The class kept Miss Dean and Jimmy busy answering questions.
          One of the boys said: “I know about caustic potash from my chemical set. See, here is a bottle of it. I did not know it was called potash lye. Here is a bottle of caustic soda. So that must be soda lye.”
          Miss Dean said: “Caustic soda is used more than caustic potash in these days for soap making. It is now cheaper than caustic potash. Besides, soda soaps are hard, and potash soaps are soft. For most uses, hard soaps are better than soft soaps.”
          When the industrial science period came, Miss Dean brought out a number of bowls and wooden stirrers or paddles, and a jar of the household fat which she had melted. Then she said:
          ”I don’t think I need to tell you what we are going to do today. What must we put together to make soap?”
          Everybody said, “Fat and lye.”
          Miss Dean went on: “These bottles on the table contain some of the many fats and oils used in soap making. We have soaps made mostly of hard fats like tallow, some from softer fats, and some which are a mixture of fats and oils. Some are olive-oil soaps, others palm-oil, some a mixture of palm and olive oils. Some very nice soaps are made almost entirely of coconut oil. Cottonseed oil is another oil used in soap making. Soap manufacturers have their own special blends of fats and oils for the soaps they sell.
          ”Now, as I open this can of lye, you will see that it is in the form of white lumps and coarse powder, like coarse salt. We must not let little pieces of lye fly out and get on our skin and clothing, because it is caustic. It would burn our hands. Later we shall find out what it might do to our clothing. So I have made a solution of some of this lye or caustic soda for you, and you must be very careful when you handle it.
          ”Look at the label on this can of lye,” Miss Dean went on. “Read the directions for soap making. Notice that exact weights or measures are called for.”
          ”I see,” said Grace. “It says to use the contents of this can for six pounds of fat.”
          ”Why do we use exact amounts of fat and lye, do you think?” Miss Dean asked.
          Mildred said: “I think that if we put in too much lye, the soap would hurt our hands.”
          Jimmy said: “If we put in too much fat, the soap might be greasy.”
          ”You are both right,” Miss Dean said. “If we would have a good soap, we must balance the fat and lye so that they exactly combine with each other. That means we must follow the directions which have been worked out for us.
          ”Each two pupils,” Miss Dean went on to say, “may have a half pound of this melted fat to make into soap. You may use the scales to weigh it. How many ounces will you weigh out? Each cup of this lye solution will combine exactly with a pound of the fat. How much lye solution will you measure for the amount of fat you are to use?
          ”Now help each other with the weighing and measuring. Pour the melted fat into the bowl, add the lye. While one pupil is stirring, the other may line one of these cardboard boxes with waxed paper. In a few moments your fat and lye will blend into a smooth, creamy mass. Then it is ready to be poured into your lined box and set aside to harden. Tomorrow you may cut your cake of soap and each have half to take home.
          ”As you wash your bowls and stirrers,” said Miss Dean, “tell me whether you notice anything which might be a proof that you have made soap.”
          (What do you think the class would see which would help them to think that they had made soap?)
          ”I have a question I would like to ask,” said Jimmy. “Why didn’t we boil our soap as they did in Colonial days?”
          ”That is a good question, Jimmy. The answer is that with our strong, pure caustic soda and exact measures we can make quite good soap nowadays without boiling. The soda combines readily with the melted fat, and really keeps on combining with it for a little time after the soap is made. But a soap manufacturer boils his soap, partly because he is more sure of getting a good soap, and partly because he makes something else at the same time which he can separate from the soap. This thing is glycerin, and it is very valuable for many things. You also made glycerin when you made your soap just now, but you cannot take it out of your soap. The soap maker can, by his process.”
          ”I’ve seen glycerin,” said Mary. “Mother uses it with rose water for our chapped hands.”
          ”Perhaps I can show you with colored chalk what happens when soap is made,” Miss Dean went on. “When lye mixes with fat it really splits the fat into two parts. Let us show these parts by two squares --

One part, the blue square, stands for acids. These acids, formed from fats, are called fat (or fatty) acids. The other part, shown by the red square, is glycerin. We will let this yellow square stand for the lye. After the fat is split the lye combines with the acids to make soap. We can show what happens in this way:

Why did I color the soap square green?”
          ”Because blue and yellow together make green,” said Jane.
          ”So these squares put together show how soap is made, and why glycerin, the red square, is also formed.”
          ”And now, how many would like to go to a large soap factory, and see thousands of pounds of soap being made?”
          Everybody would!
          ”Very well,” said Miss Dean, “we will meet here at nine o’clock next Saturday morning. You may invite one or two of your family, or a friend, to go with you.”

          When Jimmy reached home that afternoon, and told his mother how they had made soap in school, what do you suppose she said?
          She said: ”Jimmy, please run right down to the grocer’s and buy a can of lye. I have a lot of fat on hand which I cannot use for cooking, and now I know what I shall do with it. And, Jimmy, if you can figure out what we save by making this soap, instead of buying the same number of pounds, you may have the money for your bank.”

Something else for you to think about:

Find out where palm oil, coconut oil, and cottonseed oil come from.

What is soda lye made from?

What is glycerin used for? What is nitroglycerin?

Why was the soap which was made at home in Colonial days soft soap? Why are most of the soaps nowadays hard? Tell some reasons why you think it is more convenient to buy and use hard soap.

If Jimmy's mother bought one can of lye and made nine pounds of soap from it and the fat she had on hand, how much money did she save? What prices will you have to find out before you can answer this question?

A little chemistry:
What is the first change which takes place in fat when lye is mixed with it?
After this change takes place, what is it which combines with the lye to make soap?
Besides soap, what substance is also formed in soap making?
Why was Miss Dean careful to have exact amounts of lye and fat for soap making?
Tell in your own words how Miss Dean's class made soap.

Internet Links to Help you on your Way

The Chemistry of Lime and Lye
How is Soap Made? A Simple Chemical Solution.

Glycerin
Make your own Toothpaste

Nitroglycerin
Alfred Nobel invents Dynamite
Nitroglycerin: Good for Your Heart
(What does all this have to do with soap?)

Where would you like to go next?