Coconut to Soap, The Science of Oils and Saponification
This is a great science activity that lets kids start with a coconut and finish with a bar of soap.
Safety: Adult supervision a must! When handling the lye proper gloves and eye protection are necessary.
You will need: Coconuts, water, pans, spoons, strainers, bowls, coffee filters, stove, blender, lye (sodium hydroxide), balance to measure mass
Now try this:
To pull the oil out of the coconut:
1) Remove the meat of the coconuts and place in blender, covering half the amount with hot water, and blend to a puree.
2) Place the blended coconut mixture into a strainer over a bowl, straining as much liquid out of mixture as possible.
3) Place the strained liquid into the fridge overnight (or on a cool counter) to separate off the oil component of the liquid. You should see this as a solid layer that forms.
4) Remove this top solid layer (coconut oil) and place into a pan. Heat this for 30+ minutes on low to medium heat. You will start to see a small amount of solid particles darken in the heated oil. Do not allow the oil to overheat by smoking.
5) Carefully strain the oil through a coffee filter. You will use this oil to make the soap.
To make the coconut soap (this makes a small amount per kid):
1) Wearing protective gloves, eyewear, and good ventalition: Prepare a sodium hydroxide solution by placing 34.3 grams of lye into 89.0 grams of water (always place lye into water). Mix well and avoid any skin contact (rinse with lots of water if skin contact). Allow this solution to cool to about 80 degrees F.
2) Heat 234 grams of coconut oil gently, no higher than about 80 degrees F.
3) Slowly add the sodium hydroxide solution to the oil and mix well until the combination begins to whiten and thicken. This is called getting to “Trace.” This may take 20-40 minutes of mixing and letting it settle, mixing and letting it settle… until it has a very high viscosity but can still be placed into molds to form.
4) Place into a mold or place to cool. You have your soap! (Note: For good results, take soap out of molds after 24 hours. Then place soap in a place it can have exposure to air to cure. This might take several days.)
The science of making soap is called Saponification. The compounds are complex, but the science isn’t too complex. Oils are often termed tryglycerides based on the fact that their glycerin molecules have three things attached to them, namely three fatty acids. With the addition of the sodium hydroxide (which is a base – opposite of an acid), the fatty acids combine with the sodium hydroxide to make soap molecules (soap salts). What makes soap so fantastic for cleaning is that it loves water and things that dissolve in water, and it loves oils. Thus soaps are good and bringing in lots of different compounds into water and dissolving them, removing them from anything being “cleaned.”