As with preservatives, there is no point adding synthetic colorants when you have an array of natural options from which to choose.
There is a wide range of Botanics to color your soap, they come in a variety of formats (powdered, whole, or cut and sifted to remove the larger chunks) and can be used in a number of ways.
You can either add them at trace, after any essential oils which may also affect the base soap color, or you can infuse one of the liquid oils with the colorant.
Olive oil is a good base for infusions, but the process works equally well with other oils; simply heat the two ingredients over a low steady flame until the oil reaches the desired color, then drain to remove any grainy bits.
Be careful not to apply too much color or you will find the soap stains your skin, the bath and any towels – the lather should always appear white, no matter how vibrant the color of the bar. Store any colored soaps in a dark place as they can fade in bright light.
Experiment with your own coloring ideas, but here are a few common ingredients, grouped by color, to get you started.
This ancient plant has been used in many ways for thousands of years and the powder of safflower can be added at trace – about one to two teaspoons per pound of oil – to give a delicate light yellow tinge to your soap.
This common cooking spice will give your soap a warm, deep yellow color. Add a small amount – about a quarter of a teaspoon per pound of oils – at trace for a bright yellow soap.
The seeds of the tropical achiote trees are used to produce a mild yellow to bright orange colorant for food and beauty products, while the scent is warm and peppery, with a hint of nutmeg. Infuse the seeds in olive oil at one to two teaspoons per pound of oil, depending on how strong you want the color to appear.
Madder root powder
This plant root has been used to dye fabric for thousands of years, dating back to Tutankhamen’s tomb. The madder root powder is one of the best natural red colorants used in beauty products and will stain your soap anything from light pink to rich red, depending on how much you use. Just add one tablespoon per pound of oil at a light trace for a vibrant colour that works well when swirled against a white background.
Moroccan red clay
This red clay will give your soap a stable solid red hue when used at one tablespoon per pound of oils. Moroccan red clay can be mixed with other similar shades for a unique result.
Red sandalwood powder
For a striking soap color, try red sandalwood powder and achieve anything from a purplish red to deep maroon. Use a small amount – only a half to one teaspoon per pound of oil – and be aware that the colorant can react substantially to the PH level of your product; a lower PH level will result in a redder variant, while a higher PH level results in a more purple shade.
Also known as Dyer’s Bugloss, this plant is a member of the borage family whose roots are commonly used as a red dye. Depending on how much you use, and what the other ingredients are, the color achieved will vary from a pinkish-red to a bluish purple. For optimum results, infuse two tablespoons of alkanet root per pound of olive oil and use as normal.
Dried burdock is traditionally used in herbal medicine, while the seeds inspired the invention of Velcro, but burdock leaf used as a dye will color your soap with an organic green hue. Simply add a few leaves to the oil for infusing and allow that to be the majority of the oil in your recipe for a deeper green. A similar effect can be achieved using the comfrey leaf, another important herb in organic gardening, instead of burdock, while nettle leaf produces a shade of green closer to lime. A dandelion leaf can also be used for a wonderful natural color – it can either be infused or added at a light trace in powdered form, at one to two tablespoons per pound of oil.
Spirulina is a natural algae which is high in nutrients and protein, and the powder will give your soap a beautiful bluish-green hue. Infuse your oil with the powder, or add one to two teaspoons to your mixture at trace, to get a really organic-looking soap.
Indigo is a plant that has a blue dye in it which has been used to color hair, skin, textiles and beauty products for thousands of years. It is a very powerful colorant, so use it incredibly sparingly – just a quarter to half a teaspoon per pound of soap at trace will create a beautiful denim hue in your soap.
Another blue colorant, woad powder will produce a sky blue – again, use sparingly, from a quarter to half a teaspoon per pound of soap depending on how intense you want your soap to look.
Natural cocoa powder
Add one teaspoon of natural cocoa powder per pound of soap at trace for a warm brown colored soap with a truly delicious scent. The result will be a luxurious soap which adds an almost-edible indulgence to bath time.
Black walnut hull powder
The black walnut is well-known for its medicinal properties and the hull, or dry outer shell, is rich in iodine and will give your soap a deep brown color. As it is so strong, you only need to add a small amount – just a quarter to half a teaspoon per pound of oil – at trace to achieve a light or deep brown color respectively.
Activated charcoal powder
This natural soap colorant is made from burning pure, untainted organic substances, such as coconuts or certain woods, without using any chemicals. It will give your soap a deep black color and can either be used on its own, or swirled against other bright colors. A typical recipe would include one tablespoon of activated charcoal powder per pound of oils, added at the beginning of trace, to prevent the lather from becoming black.