Things You'll Need
Sharp knife or cheese grater
Heat-resistant glass measuring cup or bowl
Non-metal mixing spoon
Colors or fragrances (if desired)
Thick rubber gloves
Many people enjoy making homemade lye soap. When you make your own soap you know exactly what ingredients are in the soap, and you have the freedom to make your soap any shape, color and fragrance you like. Homemade soaps can also make an inexpensive, personalized gift for friends and loved ones. If your soap is too lye-heavy, however, it can have spots that are white or cloudy, or be hard, brittle and crumbly. Since lye is caustic, lye-heavy soap is also irritating to the skin. If your homemade soap is too lye-heavy, check the recipe you used to see what might have gone wrong. Instead of throwing away the lye-heavy soap, you can rebatch (hand-mill) it and make it into a more balanced, non-caustic mixture.
Rub a small amount of olive oil on the insides of your soap molds; this will make it easier to remove the finished soap.
Slice the soap into small, thin pieces or grate with a cheese grater. Put the soap pieces in the glass measuring cup or bowl.
Sprinkle the soap with milk, herbal tea or water. Use a few drops to 2 teaspoons of liquid per 100 grams of soap, depending on how dry your soap is.
Mix until the soap is well-coated, cover and set aside. Let the soap soak for at least 2 hours, or overnight. The drier your soap is, the longer it will need to soak.
Place the glass container in a saucepan and add a couple inches of water to the saucepan. Heat on medium-high until the water starts to boil, then reduce to simmer. Stir the soap occasionally until it melts. The melted soap will have the consistency of mashed potatoes or applesauce.
Turn off the burner and let the soap cool to about 140 F.
Add any colors or fragrances you wish. Mix well.
Spoon the soap into your soap molds. Wear thick rubber gloves when you work with the hot soap.
Tap gently on the sides of the soap molds to get rid of any trapped air bubbles.
Cover the top of the soap with waxed paper. Press down on your waxed paper and rub the bottom of the teaspoon over the waxed paper to make the top of the soap level.
Wait until the soap has cooled completely, at least 4 or 5 hours.
Remove the soap from the molds.
Leave the soap in a well-aired place for 3 to 8 weeks to cure. Turn the soap regularly to keep it from warping, especially for the first few days.
Wet the soap and test it with a pH strip. The pH should be no higher than 10.5.
If you’re having trouble removing the soap from the mold, put it in the freezer for 10 minutes and try again.
Make a note of the ingredients (like essential oils or colorings) you use and how much, so that you can re-create your best soaps.
Always be very careful when working with lye.
Soap that is too lye-heavy is caustic and can be very irritating to the skin. Test your soap with pH strips to make sure the pH is not greater than 10.5 to prevent this problem. The best soap has a pH between 8 and 10; soap with a pH of 10.5 should not cause burns but can still dry the skin out.