Step 1: Put on your rubber gloves. Weigh out 12 ounces of lye into the 2-cup plastic or glass measuring container. Be certain to account for the weight of your measuring container. Weigh 32 ounces (2 lb) of cold water into the sturdy glass container. Again, be certain to account for the weight of your container. Now it is time to mix the lye into the glass container of cold water. Put on your safety glasses. Because the lye will heat the water and fumes will be released, it is best to do this outside or under a ventilation fan. It is also wise to avert your face as much as possible to avoid inhaling the harsh and unpleasant fumes (the fuming will only last 30 seconds). Add the lye to the water slowly while stirring with a wooden spoon. As soon as all the lye is dissolved in the water, set it safely aside to cool.
Step 2: Weigh out the 24 ounces of coconut oil and 38 ounces of vegetable shortening into the metal kettle. Melt these oils over a low heat, stirring frequently. As soon as they have melted, remove them from the heat and add 24 ounces of olive oil.
Step 3: Keep your gloves on. This step involves getting the temperature of the lye to a range of 95øF to 98øF while at the same time getting the kettle of oils within the same temperature range. When both mixtures are within the range, combine them. Achieving this stage will require your full and careful attention. Use hot or cold water baths to either raise or lower the temperatures of the mixtures. There is a knack to doing this skillfully, and it only comes with practice. Now prepare your soap mold by greasing its sides and bottom with shortening.
Step 4: This is the fun part! Wearing rubber gloves and safety glasses, slowly pour a steady stream of the temperature-correct lye into the temperature-correct oils. Stir constantly in a relaxed circular motion until all of the lye has been added. By bringing the lye and oils into contact with each other, you are prompting a chemical reaction called saponification. Saponification is the creation of soap.
Step 5: Continue to stir for approximately 10 minutes. Eventually you will notice a subtle change in the quality of your mixture. It will become slightly thicker and will seem more homogenized and creamy. These changes are very slight, but in time you will learn to recognize them. Ann Bramson, in her book about soapmaking, writes about tracing. Tracing occurs when the soap mixture becomes slightly thick enough to trace a design on the soap surface with dribbles of soap. Thsi is the stage at which Ann recommends adding the scent oils and pouring the soap into its mold. Personally, I prefer to catch the saponification process just prior to the tracing stage. At this earlier stage you can comfortably add scent oils and dried grains or botanicals without fear of the mixture becoming too thick.
Step 6: If grains, dried botanicals, or colorants are to be included in your soap, add them now. This is best accomplished by separating approximately 2 cups of the unscented soap mixture and quickly whisking the dried goods into this small portion of soap until thoroughly mixed. Return this mixture to the soap kettle and stir. Now is the time to stir in the scent oils - do not linger! If you delay, you will have a kettle filled with soap that cooled too quickly. Add soon as your oils have been incorporated, it is time to fill your plastic mold (a shoe box sized plastic container works great!).
Step 7: Put the lid over the warm soap mixture. Set it in an undisturbed, warm place and cover well with many layers of blankets (wool seems to do the best job). Allow the soap to sit undisturbed for 18 hours to complete the saponification process.
Step 8: Remove the blankets and lid. You should now have a beautiful block of soap - firm, fresh, and fragrant. Allow it to sit uncovered for another 8 to 12 hours before removing it from the box. To remove, simply turn the box upside down and allow the soap to fall onto a towel or a clean work surface. If you have followed directions carefully, and if your scale and thermometer are accurate, you should have a beautiful batch of homemade soap. If there are quality problems, you will notice a thin layer of oil on the top of your soap and a crusty chalk-like layer on the bottom. This malady is known as separation. If the separation is minor, you need only scrape off the top and bottom layers and discard them. The ramaining soap should be fine. If gross separation has occured, you will find more than a film of oil on top of your soap. It will look more like a pool of oil. In this case, you can be certain that your scale, thermometer, or mathematical methods were in error. Unfortunately, if this occurs, you will need to discard the soap or use it for laundry purposes.
As soon as you are ready, you can cut your fresh soap into slices, bars, or chunks. You may also opt to leave it as it is and cut bars out of the large block as needed.
Should you wish to form or stamp it in any way, do this when the soap is still fresh and soft, within a few days. As time goes by and your soap begins to air dry (sure), it will become progressively harder and more difficult to cut. It never becomes too hard to cut, though this is done most easily within the first 2 weeks. This is because the water in the soap is constantly evaporation and diminishing. As the water evaporates, the soap will lose water weight and volume and can shrink as much as 10%.
A well-cured soap is exactly what you want. Not only will a well-cured soap last longer when subjected to the rigors of water, but it will also achieve its optimum mildness as it ages. Curing cam best be accomplished by simply exposing your soap to warm dry air free from dust or dirt. Cure your soap for a minimun of 2 to 3 weeks before using.
Source: "The Soap Book: Simple Herbal Recipes" by Sandy Maine