There are three different ways (that I know of) to mix soap colorants. One is with water (which only works with water-soluble colors such as FD&C, most micas, clays, and water-soluble titanium dioxide). The second way is with vegetable glycerin, which seems to work best with micas or pigments/oxides. And the third way is with oils, which will also work best with micas, pigments, oxides, and other natural colorants such as powdered herbs and cocoa powder.

So which method is the BEST method? I’ve attempted all of these, and no matter which one I’ve tried, if I am adding water, glycerin or oil to my soap recipe, it can alter the final soap. Add extra water and the soap can be sticky coming out of the mold. Add extra glycerin and the soap may never fully harden. Add extra oils and you may have the same problem – extra superfatting which can make the soap too soft.

The best solution I’ve come up with (whenever possible), is to use part of the oils from the soap recipe so that I’m not adding extra oils. This works very well with micas, pigments, oxides, and powdered herbs. The only downside to mixing soap colorants with oil is the clean-up. You have to use plenty of soap to wash up your containers, unless you are using something disposable.

What if the colorant is water-soluble? Most of the water-soluble colorants really don’t require that much water to disperse them. Especially the FD&C colors – a little goes a LONG way! Water-soluble titanium dioxide can be added to the lye water (I like to add it after the lye has heated up) to lighten an entire batch without adding any extra liquid. Even if I am only adding titanium dioxide to part of a batch, it doesn’t take more than a few tablespoons of water to dissolve it. Even clays and activated charcoal can be dispersed in water. The only time I had issues with sticky soap was when I tried to add water to micas because it took a lot more water than other colorants.

I used to LOVE using glycerin with micas and oxides because it was so easy to clean up afterwards. No soap required! That was before I ended up with a soft soap. I couldn’t figure out why it was taking so long for the Caribbean Diva soap to cure, compared to the Tahitian Vanilla. I had made them the same week! Until I remembered how much glycerin I had to use to disperse the orange mica in the Diva soap. It did eventually get hard enough to sell, and thankfully its size makes up for the fact that it’s a little bit softer than my other soaps, but I won’t make that mistake again.

Follow-up post on the subject is found here.