I’ve been asked a few times over the past couple months how I colour my soaps. One of my biggest pet peeves is seeing a store like Lush or The Body Shop branding itself as “natural”, and seeing how many artificial, petroleum-derived colourants they use in their products while still riding that “natural” marketing train.
I tend to use more natural colourants, ranging from naturally coloured oils to iron oxides. The saponification process is a bit of a wild card, in that you never know how a coloured ingredient will be effected afterwards. Apparently rosehip extract, which is bright pink, turns black turning saponification. Whoops, haha. Anyhow, here’s how I colour my soaps, without the use of any artificial dyes.
This oil is a bright, deep orange naturally. I use it in varying amounts to get anything from a nice, mellow yellow colour, to a bright, bright orange. You don’t need much of it to achieve great colour, so you can add it after trace without worrying about your superfat percentage too much. Take care not to stain your clothes with it, though! I find it holds up fairly well against fading, though it will fade quite noticeably after a year or so.
You don’t need much at all to get a nice, pastel tint in your soaps. The bonus with oxides is that you can achieve colours, like lavender or bright blue, that can be quite difficult to achieve with anything else. The negative is that you can really only get fairly soft colours—I’ve found that if you add too much it gives the soap an odd, almost mottled look, known as glycerin rivers. Bars coloured with lots of iron oxide can also leave coloured soap scum streaks on everything.
Note: Oxides fall into a strange sort-of-limbo as far as the term “natural” goes. The compounds for iron oxides and blue ultramarine do exist naturally as rust (or semi-precious stones in the case of ultramarine), but are generally contaminated with heavy metals or are very expensive, and as such the ones we purchase are synthesized.
This is probably one of my favourite ways to colour soap! I always add clay to my soaps anyways, so it’s like multi-tasking. French Green gives a beautiful green tint, Rhassoul adds brown, and so and and so forth (it’s pretty obvious which clays add which colours, and I’ve found they don’t change during saponification).
Great for making soap white (or whiter), but not great for much else. For soap making either the oil soluble or water soluble version will work, just be sure to use an immersion blender to break up any clumps so you don’t have white blobs of powder in your final bars.
I’ve had varying levels of success with this one. Blackstrap molasses works really well to get a very dark brown colour, but you have to be careful not to use too much or the sugar content can cause the batch to curdle (keep the temperature low, too). I’ve also tried simmering brightly coloured fruits and vegetables, like cranberries and beets, and then puréeing and reducing the mixtures before stirring them into the soap. That has worked, more or less, but I probably wouldn’t do it again now that I can add oxides instead, especially since the food colouring options are more prone to shifting colour during saponification (usually to something brown) and fading over time as the bars age.
This works well for getting a nice brown colour, though, sadly the scent doesn’t really come through. You can use instant coffee powder or use brewed cold coffee instead of water to add the lye to.
Spices are a great way to add colour, exfoliation, and scent at the same time! I’ve had good success adding swirls of ground cinnamon to soap. You could also experiment with other spices like paprika—just stay away from things like cayenne pepper, which will definitely wake you up during your morning shower, but not very nicely!
And that’s it! With these options you should be able to easily (and naturally) create the rainbow. There are limits, of course—you won’t be able to create super dark colours without bleeding, or neon shades, but I’ve found more than enough variety here to keep me more than happy with the possibilities!