Sneak Peek: Testing Natural Colorants

By Ruth Esteves

My latest big project is to test natural colorants in cold process soap. Lots of them. I’ve always been a little wary of using natural colorants because there isn’t one good resource that could tell me what they will look like, or how much to use, or which stay looking good. So I’ve decided to become that resource.

Here’s one of the first surprising things that I’m noticing: gelling matters.

For the non-cold process soapmakers: “gel” is that phase that soap sometimes goes through when it gets pretty warm and looks translucent, like a mold full of colored vaseline. It isn’t necessary for soap to gel in order to become soap, but I’ve always known that it will affect how the soap looks in the end. Soap that doesn’t gel tends to look creamier and more opaque, and it will take a bit longer to firm up. But that’s the only differences between the two.

So back to the surprising bit: take a look at this shot of some of my recent tests.

The bars in the left column were colored with the same thing as the ones on the right. In fact, each pair came from the same batch; I just put one on a heating pad and the other in the refrigerator. The ones on the right gelled and the ones on the left didn’t. Quite a difference, huh? This isn’t just a texture difference. Something has really happened to the color in the gelled soap that has made it darker and richer.

I’m thrilled, really. Because this suggests that I have so much to learn about natural colorants. And the only thing I like more than learning something new is teaching it! 🙂

Do you have any favorite natural colorants that you use? Or is there one in particular that you would like me to test?

UPDATE: All of this testing was bound to lead somewhere! Click here to read more about the “Coloring Soap Naturally” eBook that is available now, all about natural coloring in cold process soap. I tested 34 different ingredients and in all kinds of ways. Then I took photos of it all and organized it so you don’t have to do all the testing yourself!

27 thoughts on “Sneak Peek: Testing Natural Colorants”

  1. How do you prevent gel phase? Is not insulating the soap enough, or do you need to put it in the fridge? I’m guessing it probably depends on the batch, but if you aren’t using fragrance or essential oils, is it easier to prevent?

    Also – what have you used in the above shots? Looks turmeric, annatto, and maybe paprika? Cinnamon?

    Thanks, Ruth!

    • Hi Rose! Sometimes not insulating is enough, but for a sure-fire way just put in the refrigerator overnight. That’s what I did. It’s easier to prevent if none of your ingredients naturally speed up the saponification. Some fragrance and essential oils do, like you mentioned. But also be careful with honey or any other sugar. I put those in the freezer, just to be extra sure!

      The colorants above are (from the top) pink kaolin clay, rose clay and paprika.

    • Ah, yes. I’ve already tested a bunch of greens, and I’ll be seeing how they hold up after I take them out of my dark curing closet. Some of them are so pretty right out of the mold. I hope they hold up. I’ll be sure to include parsley powder, too!

      • Have you ever tried any of the seaweeds – spirulina or kelp powder? I’ve heard they hold up well, but can leave a fishy scent behind – something you’d probably want to cover with a good EO or FO.

      • Yes, I have tried both of those added at trace. I preferred the spirulina, but I want to try with more kelp powder again. I went easy on it the first time because of that smell issue. Which EO do you think would be good with “fishy”? Maybe something strong, like eucalyptus or fir needle?

      • I just unmolded a very, very green soap made with powdered nettle leaf. When I first cut into it, there was sharp herbal smell, but it seems to be fading rapidly. I scented the batch with a heavy pine fragrance oil – it’s beautiful! I think it would definitely do to cover any kind of fishy odor. Another one to try would be anise and lime – that’s a classic “fisherman” kind of scent, I think.

    • Hi Inbal, I don’t let milk soaps gel because the heat can cause the proteins and sugars to burn, making the soap tan or light brown. And natural orange? I like the paprika (the bottom soap in my photo). Also annatto and unrefined palm oil will give you shades from yellow to orange, depending on how much you use.

      • Huh. I never thought about the sugars in milk and gel phase, but so far I’ve made two batches with coconut milk added at trace, and haven’t had any discoloration issues. Maybe it doesn’t have the same sugars as animal milks?

      • I should have been more clear. I think that sugars tend to make it more likely that a soap will go through a gel phase, and get hotter. This heat can then cause not only the sugars but also the proteins to turn the soap tan. I haven’t tried coconut milk, but my guess is that both the sugars and the proteins are different (and in lower concentrations, maybe?) from cow or goat milk. That may explain the difference.
        Also many times milk soaps are made with only milk (no water,) and so there you have again more sugar and protein present compared to adding a smaller quantity of milk at trace.

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  6. I’ve experimented a lot with gelled/ungelled clays in soap and the difference is great. As in: pastel vs deep hue. Your image of the experiment is great and really shows what heat can do to a hue 🙂 Natural colorants that are not greatly affected by gelling are indigo, elderberry and nettle

  8. I know this is an old post, but this is really wonderful-I’ve never done this sort of test before, and didn’t realize the could be such a huge difference! Wow!

  10. Dandelion leaves make for a fabulous bright green color, plus they have great health benefits for the skin. I love using those in my soap making, so if you are still looking for a natural green colorant, you might like to try that!

  11. I am a newbie in soap making and have a question about gelling. can I recipe that contains coconut milk be set to gel? thanks

    • Yes, you can, marianella. Just be aware that letting a milk soap gel will usually cause the color to be less creamy white and more tan. But otherwise, it’s not a problem at all.

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