Natural Soap Colours: A Guide to Plant-Based Colourants

Natural soap colours offer a beautiful alternative to synthetic dyes and artificial colourants. Made from plants, flowers, roots, clays and minerals, they allow soap makers to create a wide range of earthy, soft and vibrant shades while keeping their ingredients as close to nature as possible.

For Australian soap makers who prefer natural and organic ingredients, choosing the right colourant is about more than appearance. It is also important to understand how each ingredient behaves during soap making, how it reacts with the high pH of soap and whether its colour will remain stable over time.

Whether you are making handmade soap for personal use or developing a natural skincare range, there are several ways to add colour without relying on synthetic additives.

What Are Natural Soap Colours?

Natural soap colours are colourants derived from natural sources rather than manufactured synthetic dyes. They typically come from botanical ingredients, mineral pigments, clays and other naturally occurring materials.

Common natural colourants include:

• Plant powders: Turmeric, spirulina, alkanet root, madder root and indigo.

• Clays: French green clay, pink clay, yellow clay and Australian kaolin clay.

• Botanical ingredients: Calendula petals, cocoa powder, coffee and activated charcoal.

• Mineral pigments: Naturally occurring iron oxides and other mineral-based colourants suitable for cosmetic use.

Each ingredient produces a different result. Some create subtle pastel shades, while others give soap a deeper, more dramatic colour.

One important consideration is that natural ingredients do not always produce exactly the same shade. Growing conditions, harvesting methods, processing and storage can all influence the final colour.

10 Natural Ingredients for Colouring Handmade Soap

There is no need for artificial dyes to create attractive handmade soap. Here are ten natural ingredients commonly used to colour cold-process and other types of handmade soap.

Different natural ingredients create different shades. The following table provides a general guide to the colours you can expect.

Keep in mind that these are indicative colours rather than guaranteed results. The final shade depends on the recipe, colourant concentration and curing conditions.

How to Add Natural Colours to Soap

The way you introduce a natural colourant can make a significant difference to the finished soap. Some ingredients dissolve or disperse more easily in oils, while others are better mixed with a small amount of liquid.

Here are three common methods.

1. Oil infusion

This method works well with botanicals such as alkanet root and calendula. Add the dried plant material to a suitable carrier oil and allow it to infuse before straining and using the coloured oil in your recipe.

2. Mixing powders

Fine powders such as turmeric, cocoa and spirulina can be dispersed in a small amount of liquid or oil before being added to the soap mixture. This helps minimise lumps and uneven colour distribution.

3. Adding clay

Clays are usually mixed with a small amount of distilled water or liquid oil to create a smooth paste. This makes them easier to incorporate into the soap batter.

Are Natural Soap Colours Better Than Synthetic Colours?

Natural and synthetic colourants both have advantages, and the right choice depends on the type of soap you want to make.

Natural colourants are attractive to makers who prefer botanical and mineral ingredients and want to avoid synthetic dyes. They often create softer, more organic shades that suit handmade skincare products.

Synthetic cosmetic colourants, on the other hand, can offer brighter colours, more predictable results and better batch-to-batch consistency.

For natural soap makers, the main challenge is finding ingredients that balance appearance, stability and suitability for the intended cosmetic application.

It is also worth remembering that natural does not automatically mean safer. Botanical ingredients can cause sensitivities, and not every pigment or powder is suitable for use on skin. Always select cosmetic-grade materials.

Are Natural Soap Colours Safe for Skin?

Natural colourants can be suitable for handmade soap, provided they are carefully selected and used at appropriate concentrations.

Before using a new colourant, consider:

• Whether it is cosmetic-grade and suitable for rinse-off products.

• Whether it is free from unwanted contaminants.

• Its recommended usage level.

• Its behaviour in high-pH soap.

• Potential skin sensitivities or allergic reactions.

In Australia, cosmetic products must also comply with applicable ingredient, labelling and product safety requirements. 

Why Do Natural Soap Colours Fade or Change?

One of the biggest challenges of using botanical colourants is colour stability.

Unlike many synthetic pigments, plant-based colours can be sensitive to environmental and chemical conditions.

Several factors can affect the final shade:

• High pH: The alkaline environment of soap can change the colour of certain botanical pigments.

• Light exposure: Some natural colours fade when exposed to direct sunlight.

• Heat: Excessive heat during processing or storage can affect colour stability.

• Oxidation: Exposure to air can gradually change certain plant-derived pigments.

• Ingredient quality: Different harvests and batches of botanical materials can produce different results.

To maintain colour quality, store finished soap in a cool, dry place away from direct sunlight. Test new colourants in your own recipe and assess the colour after curing, not just immediately after pouring.