One of the most confusing experiences when working with natural soap colors is watching a beautiful color in your soap batter turn into something completely different once the soap finishes saponifying.
This is called color morphing, and it’s very common when working with botanical colorants.
The truth is that sometimes color morphing cannot be prevented. Soap is a high-pH environment, and many plant pigments simply cannot survive that chemistry. When those pigments encounter alkalinity, heat, and oxygen during the soapmaking process, they change.
Understanding which botanicals are stable — and which ones are not — is the real key to preventing unwanted color morphing.
Why Natural Soap Colors Morph
Cold process soap is an alkaline environment, usually around pH 9–10. Many plant pigments evolved in acidic or neutral environments, so when they encounter the alkalinity of soap, their chemistry changes.
Heat generated during saponification can also alter plant pigments. Some colors darken, some fade, and others shift into entirely different hues. This is why a botanical that produces a gorgeous color in tea or an oil infusion may behave very differently once it is added to soap.
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Some Color Changes Cannot Be Prevented
Sometimes color morphing simply cannot be prevented.
A classic example is butterfly pea flower. It produces stunning blues and purples in teas and infusions, but when exposed to the high pH of soap, those pigments often turn brown. This isn’t a mistake in your process. It’s simply how that plant pigment behaves in an alkaline environment.
When this happens, the best solution is not trying to force the botanical to behave differently — it’s choosing a botanical that produces the color you want in soap.
Choosing Stable Natural Soap Colorants
Instead of fighting color morphing, many soapmakers learn which botanicals reliably produce stable colors in soap.
For example:
- Indigo produces reliable blues in soap.
- Alkanet can produce beautiful purples when properly infused.
- Turmeric produces stable yellows and warm oranges.
- Charcoal creates dependable gray and black tones.
Choosing botanicals that are known to perform well in soap will save you a lot of experimentation and unexpected results. If you’d like to explore more botanicals that work well in soap, you can browse my Botanical Soap Color Index:
Understanding How Colors Morph: Alkanet Examples
Alkanet is a great example of a botanical colorant that does morph, but in a predictable and useful way.
Alkanet infusions often begin as a soft mauve tone in fresh soap batter. As the soap cures, the color can deepen and shift toward blue-purple or purple depending on the formulation and infusion strength.
If your alkanet soap turns gray instead of purple, the most common causes are:
- the infusion is too weak
- the alkanet root is low quality
- not enough infused oil was used in the batch
Using a strong infusion of high-quality alkanet root typically produces much better purple results.
If you’d like to dive deeper into working with alkanet and anti-alkanet blends, you can explore the lessons inside my Alkanet and Anti-Alkanet Master Class.
Testing Botanicals Before Making Soap
If you’re experimenting with new plant colorants, a quick lye test can help reveal how a pigment will react in soap.
This simple test exposes the botanical to an alkaline environment before you make a full batch of soap. If the color shifts dramatically during the test, it’s a good indication that it may morph in soap as well. Testing botanicals ahead of time can save you from making an entire batch that turns into a color you didn’t expect.
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Working With Natural Color Changes
One of the most rewarding parts of natural soapmaking is learning how botanical pigments behave.
Instead of trying to prevent every color shift, many soapmakers learn to work with those changes. Some botanicals deepen in color as soap cures, others soften into earthy tones, and some create surprising new shades along the way.
Once you understand how different botanicals react to soap’s chemistry, designing beautiful natural color palettes becomes much easier.
Happy soaping. 🧼
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