How to Test Soap Colorants

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I was lucky to help Lori with testing different kinds of soap colorants. She was preparing for a presentation at the Handcrafted Soapmakers Guild Annual Conference called “Coloring With Confidence”: a survey of over 70 different kinds of soap colorants: oxides, ultramarines, herbs, spices, lakes, dyes… It was a great presentation with loads of great information.

Anyway, this all got me thinking that what would really help me is to know how much of my colorants to use to get the shade that I want. I typically use oxides, ultramarines and micas. I don’t want to use too much and waste it (or worse, get colored lather – especially red – ewww) or use too little and not get the effect that I want. So I’ve designed a procedure to test different concentrations of my colorants. I have used it to test four different colors so far and am happy with the results.

Step 1: Decide what to test.
Pick which concentrations you want to test. Four different concentrations seems to give a good range of color. I recently tested some oxides at 1 teaspoon(tsp) per pound of oil (ppo), 1/2 tsp ppo, 1/4 tsp ppo and 1/8tsp ppo. The same concept can be used to test other colorants (that may need more or less) by adjusting the amount added to each sample.

Step 2: Prepare your containers.
I used paper cups as soap containers and prepared them by labeling them with the colorant and the concentration for each cup. This picture shows the cups for testing 3 different oxides in 4 concentrations each. (I was feeling productive!)
Step 3: Make a 1-pound batch of unscented soap for each colorant that you’re testing.
Since some scent will affect color, it’s best to start with no scent. Calculate the total volume of your soap batch (depending on your lye and water amounts) and divide by 4. This is the amount that will go into each cup.

Step 4: Add colorant to each cup.
Remember, the amount of colorant that you want to add is enough to get the right concentration in 1/4 pound per oil. So, in my example, the first cup gets 1/4tsp of colorant (because I want the concentration to be 1tsp ppo and I’m going to put in 1/4 pound of soap, right?). The cup labeled 1/2tsp ppo gets 1/8 tsp of colorant and so on. Hint: if you are using a dry colorant, like oxide or ultramarine, it’s a good idea to suspend it in a little water and blend it before going on to the next step.

Step 5: Add 1/4 of your batch of soap to each cup and stir, stir, stir until the color is blended evenly.

Step 6: Cover containers and leave to saponify.

Step 7: Rip off the paper cup and admire your colorful soap!
This would be a good time to take a picture, too.

Step 8: Label your soap by carving in the concentration with a dull pencil or skewer.
This is my result from 1/2tsp ppo of burgundy oxide.

One final note: if you were paying attention and doing the math along with me, you will have noticed that the last cup in my series (the one with a concentration of 1/8tsp ppo) would have needed 1/32 tsp of colorant. That’s a very small amount to measure accurately. Often, you’re lucky if you have a 1/8tsp measure in your measuring spoon set! How I got around that was to take one half of the soap in the 1/4tsp ppo (once I had colored it) and put that in the 1/8tsp ppo cup. Then I added an equal amount of uncolored soap and, TA-DA!, soap at 1/8tsp ppo. I end up with less of that 1/4tsp ppo soap (you can see that clearly in the picture of the soap in the cups above) ,but it is still plenty to keep as a sample.

I hope that this is helpful and that I have encouraged you to try it for yourself. Remember, it can be used not just with oxides, but any kind of colorant: other pigments, micas, clays, herbs, dyes. It takes some planning and time, but I expect that I’ll be referring to the results of these trials over and over again.

I would love to hear what you think if you try this method, or if you come up with another method of your own!

Note – want to see the results of Ruth’s testing? Check out her awesome Coloring Soap Naturally eBook!


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