Making Soap
"It is not the style of clothes one wears, neither the kind of automobile one drives, nor the amount of money one has in the bank, that counts. These mean nothing. It is simply service that measures success." George Washington Carver
One of the most common needs of people is soap. Keeping our hands and bodies is essential to good health. Soap removes dirt and germs better than plain water. We can learn how to make soap in this lesson. All we need are ashes, water, and fat!
Part 1: Making Lye
In this part of the experiment we will use ashes and make lye.
Materials Required
• Paper towel
• Water
• Cups
• Screen
Procedure
1) Find ashes from a wood stove or fireplace that are dead and cold. Be sure that ashes are always transported in a metal container, just in case.
2) Use a screen to filter the ashes. This can be done in a variety of ways. A piece of window screen can be placed in the opening of a canning lid and screwed to the jar. Ashes can be placed in the jar and then “shaken.” A screen over a tub can also be used.
3) Screen out about 200 ml of ashes onto a piece of newspaper or scrap paper. Ashes are messy so make sure to do this process carefully so as to not create too much dust.
4) Place the ashes in a jar, bowl, or other container and pour in 200 ml of water. Allow this to soak overnight.
5) The next day, prepare a piece of good paper towel as a filter. Fold the paper towel to make a filter as shown below:
6) Make a funnel. You can make a funnel from the top of a 2 liter plastic soda bottle.
7) The water will have dissolved some lye (sodium hydroxide) from the ashes as it sat overnight. Pour this water into your funnel lined with filter paper. The water that is filtered out of the ashes will contain sodium and potassium hydroxide (lye). In high concentrations this material is very caustic. The amounts that will be generated in this experiment are not terribly hazardous, but they should be treated with special caution. Gloves and eye protection are recommended, but not absolutely essential. Students should not allow the solution to stay on skin. If they do get any on their skin it should be washed off thoroughly. Set aside the solution in a container marked: “Sodium and Potassium Hydroxide: Weak solution.”
Part 2. Making Soap
In this exploration we will take the lye, add it to oil, heat, stir and make soap!
Materials Required
• Oil or fat from any food source
• Lye solution from above or use Drano or similar solution. (Note: Lye solution is caustic. This should be done carefully and under supervision. Use plastic gloves and eye protection.)
• Stove and pan from Making a Stove and Cup exploration.
Procedure
1) To make soap, oil or fat is mixed with sodium hydroxide. A chemical process called saponification occurs which rearranges the fat molecules to make them “slippery.”
2) Before we mix each liquid, prepare a piece of ordinary writing paper for an experiment. Divide the paper into four equal sections by folding or drawing lines. Place one drop of Sodium Hydroxide on one quadrant and one drop of vegetable oil on another quadrant. Note the way the paper looks after each liquid dries.
3) Place about 20 ml of vegetable oil in a glass container. Add the same volume of Sodium/Potassium Hydroxide. Observe each liquid carefully noting color, texture and behavior.
4) Cork or cap the container and shake vigorously. Pour the liquid into a pan, heat gently and stir.
5) Observe the mixture. Note changes in the liquids.
6) Place a drop of the mixture on the paper. Feel the mixture between your fingers. Describe the way it looks and the way it feels. Is it a fat? Is it still Sodium/Potassium Hydroxide?
7) When the mixture cools, add a small amount in a test tube and add water. Shake vigorously. Observe bubbles and foam? What do these indicate?
Discussion
To understand how soap is made chemically, we need to understand a process called saponification.
Fat. We first must have a little information about fat. Fats and oils are the basis for soap. Fat is a large molecule of carbon, hydrogen and oxygen. It is manufactured by plants and animals as a way to store energy and as essential nutrient for healthy digestion and cellular function.
Fats are not soluble in water. When you get butter or margarine on your hand, plain water is not able to remove it.
Fats are made by the animals as a way of storing food energy. The animal takes unused protein, carbohydrate or fats it eats and converts it into a special molecule called a fat. Fats are made up of long chains of at least 16 to 18 carbon atoms attached to a 3 carbon molecule called a glycerol.
Fats are organic compounds because they are synthesized by plants and because they have multiple carbon-hydrogen-oxygen bonds. Organic compounds can be made in a laboratory using a variety of methods, materials and processes.
Lye. An inorganic compound generally does not have C-H-O bonds. Minerals, salts, alkalis, acids are inorganic compounds. One particular inorganic compound that is found in nature is called lye. The chemical name for lye is Sodium Hydroxide. Most people are familiar with lye because it is the active ingredient in a household product like Drano.
Sodium Hydroxide is a chemical composition of sodium, hydrogen and oxygen in the following configuration.Na stands for sodium, O-oxygen, H-hydrogen. The molecule is simple and highly reactive. When this dry chemical is mixed with water it ionizes--the positive sodium atoms separate from the negatively charge OH molecules. Anything that comes in contact with this solution is subject to the highly reactive sodium atoms.
That is why Drano is so effective in cleaning out a sink trap. The active sodium atoms go to work attacking almost any other molecule that it comes in contact with, especially organic compounds. That is why it is harmful to humans to get on their skin--it digests it!
A sodium hydroxide burn. Caution!
Saponification
If sodium or potassium hydroxide (lye) is added to a fat, it changes the fat molecule. A fat molecule added with sodium hydride and a little heat will form a chemical reaction called saponification. What is left are two new molecules that give soap its characteristic slipperiness.
Saponification rearranges the atoms in the fat molecule. “Sapo” is the Latin for soap. Soap making is an ancient art and science. See http://waltonfeed.com/old/soap/soap.html#lye
The methods of soap making are ancient and were repeated through history. Today, many people enjoy making their own soap.