You can make your castile soap as colorful and as lovely scented as you’d like. You can literally make this recipe with just three ingredients if you choose — water, lye, and olive oil. The optional lavender essential oil will give it a beautiful floral scent and the sodium lactate or salt helps to harden the bars.
Although listed as 'optional', sodium lactate is useful in hardening all soap recipes, especially softer soap like this castile soap recipe. It's available as a powder or in liquid form and if you're using the liquid form, you'll need one teaspoon of it.
Some people find pure Castile bar soap to be “slimy” and not cleansing enough. On the other hand, pure coconut oil bar soap can be drying. Pure coconut oil soaps are great for general cleaning and for laundry. That’s why I made my homemade laundry soap only with coconut oil.