Soap Bubbles, Chapter 18

          The class knew it was to be the last lesson on scourers, and there were two things they wished to do. Do you remember them?
          Miss Dean had remembered, for there was a row of scourers on the table, with a little saucer in front of each, and there was a bottle of vinegar. There were also some other things, but the children did not find out what they were to be used for until later.
          “Oh, I know what the vinegar is for,” said one of the boys. “We are going to test for carbonates.”
          “We are,” said Miss Dean. “You may each put a little scourer in these saucers, and place the package behind the saucer so that we shall know which scourer you are testing. Here are knives for scraping some powder from the scouring soaps, and spoons for taking out some of the pastes. The liquid polishes we will leave at one side to talk about later. Today, you know, we are to try to find out what else may be put in scourers besides soap and abrasive.”
          Presently each child had some of his scourer in a saucer, and the vinegar bottle went from hand to hand. Everybody watched each saucer as the vinegar touched the scourer.
          “Mine fizzes!” “And mine.” “And mine.”
          One after another the children called out what was happening in their saucers, and nearly every scourer was found to fizz.
          Mary say, “My tooth powder and tooth paste foam up too when mixed with the vinegar. Do they have a carbonate in them?”
          “Take a piece of chalk from the blackboard and drop it in vinegar,” said Miss Dean. “If it is real chalk it will fizz a little in the vinegar. So that would show chalk to be a carbonate, would it not?”
          “You said the shells which make chalk contain lime, didn’t you, Peter?” asked Miss Dean. “So we shall have to call chalk lime carbonate. That is why your tooth powder and paste fizz, Mary.
          “Many of these scourers contain chalk or whiting, which also is chalk, you remember, and the acid will make it foam up. But often some sodium carbonate is added to help the scourer clean greasy surfaces such as cooking vessels, and then a great deal of foam is made when the vinegar touches the scourer.
          “So,” Miss Dean went on, “while the main part of every scourer is the abrasive, it usually contains soap and often sodium carbonate. The soap and soda help to remove the particles of grease or dirt or tarnish that the abrasive scours off.”
          “What do these cans of metal polish contain?” asked Jimmy.
          “Shake up several of the cans and pour a little in these clean saucers,” said Miss Dean. “Rub some between your fingers.”
          “I can feel the abrasive,” said Jimmy, “and something which feels like an oil.”
          “That is what many metal polishes contain,” said Miss Dean; “an abrasive, and usually some soap, and a liquid to help spread the abrasive over a surface and make a smooth polish. The liquid which you are feeling, and which you say feels like oil, is probably something like gasoline. Read the label and see if it warns against fire.”
          “Yes, it does,” said Jimmy.
          “Then it is gasoline or a similar liquid which takes fire readily. We must always read the label when we use a can of liquid scourer, to see whether we must be careful about fire. Do the other cans have the same warning on their labels?”
          “Not all of them,” said Jimmy. “This says ‘noninflammable.’ I suppose that means that it will not burn.”
          “Right,” said Miss Dean. “Smell of the liquid in this can and see if you can tell what it is.”
          “I know that smell,” said several. “It is ammonia. We have it at home in bottles in the kitchen.”
          “So we might go on,” said Miss Dean, “and find different odors, because it is the kinds of liquids which are mixed with the abrasive which make the real difference in these liquid metal polishes. If we knew more about metals. we would find that we would know better how to choose between these kinds of metal polishes, but just now we must choose by the fineness of the abrasive.
          “And now, we are going to make our own scouring soap for silver and fine metals.
          “We are to use about equal weights of soap and abrasive,” said Miss Dean, “and mix them well in this large kettle. Read the label on this package of flake soap and find out how much the contents weigh.”
          “About fifteen ounces,” said Mary. “It says ‘net,’ and we know that means without the package.”
          “Very well,” said Miss Dean, “then we shall need to weigh out on these scales about a pound of abrasive. I have here a package of very fine whiting, called floated whiting, which makes a good silver polish. Weigh out a pound of it; how many ounces will you have?”
          “Sixteen,” said several.
          “Now empty the soap from the package into this large saucepan, and we will add just enough hot water to make it into a smooth paste. Please take turns stirring until it is perfectly smooth. Now we are ready to stir in our whiting, and those who have not helped stir the soap may take turns doing this.”
          Miss Dean then brought out a bottle marked “glycerin,” a name which the class remembered from their soap lessons.
          “I will ask Grace to measure out three tablespoonfuls of glycerin and add to our scouring soap,” she said. “It will help bind the soap and the abrasive together, and keep the scourer from drying out too fast. And now I am going to add a few drops of oil of wintergreen. It is not really necessary, but it does help to keep the scourer in good condition. Some other oil, similar to oil of wintergreen, such as oil of peppermint or oil of lavender, would do as well.”
          By this time the steady stirring had turned the mixture into a creamy paste. Miss Dean then said:
          “Each of you may take one of these little jelly tumblers. Fill it with your new scouring paste and take it home. Then try it on your silver or nickel or porcelain, and let us know how well it does its work.”
          “Does our polish cost as much as the silver polish we buy?” asked practical Peter.
          “That is a good question,” said Miss Dean. “Let us find out.”
          So the class added up the cost of the soap and the whiting and glycerin, as Miss Dean gave it to them. They found that with the water they had used they had made nearly three pounds of scouring paste. The next thing to find out was how many ounces of paste there were in one of their jars of silver polish, and how much it had cost. Then they thought they were ready to say that three pounds of the paste they had bought would cost a great deal more than the paste they had made.
          “But you must remember the cost of the glasses in which you have put your paste, and the value of your time in making it,” said Miss Dean.
          The value of time was a new idea to the children, but Miss Dean explained that the manufacturer had to count this and many other things in the total cost of his product.
          “This scourer that we have made is good,” went on Miss Dean, “and of course it does cost less than the ones in the store, but it is probably not so good as those made by people who have studied for years how to make the best possible scourers for certain uses.”
          “Well, we like our scourer, anyhow,” said several children, “and we have liked talking about scourers.”