Cover all surfaces with newspaper before you start, and make sure there are no kids or pets around while you work with lye. You should wear gloves and protective eyewear as well.
Add your oils to the glass container and microwave to liquify them. This can take a minute or more, depending on your microwave. Oils need to be liquid and at room temperature to make soap. Let the oils cool in the container or bowl as you move on to the next step.
Add your water to the glass container, then sprinkle on the lye you measured out. Never add water to lye – doing this can cause a volcano effect or a spill. Stir the mixture for a moment, then let it sit, it will get hot; this is the chemical reaction between the lye and the water that creates the lye solution.
Pour the lye water into the bowl with the oils and stir gently to combine. Use a stick blender or immersion blender to blend the oils and water together. As you blend, they will come to trace, which is essential for soapmaking. Trace refers to the texture of the mixture. It will look like a thick pudding when you’ve mixed it enough.
Add your fragrance and any additives. Be prepared to work quickly. Some fragrance oils accelerate trace and firm the mixture up too much to pour.
Pour the prepared mixture into your mold. Cover the mold with plastic wrap, then insulate with a towel or blanket. Leave covered and undisturbed for 24 hours. This will also create glycerin for moisturizing.
Remove the soap from the mold and slice into bars.