There are so many different types of colourants available that it can be difficult to choose which one to use to achieve the desired effects. Hopefully the following information will help you to decide which ones to use for your particular project.
Dyes: FD&C colourants (Food, Drug and Cosmetics) fall into this category. They are colour additives which are soluble (dissolve) in water, oils, alcohol or glycerin. Characteristics of dyes: they produce very bright, intense colours, but they do bleed/migrate in soap and they are usually unstable in cp soap. They are generally inexpensive to use as they are extremely concentrated and they mix in smoothly so are easy to use.
Oxides and Ultramarines: These are colour additives which are insoluble in the medium to which they are added (does not dissolve in water or oil). They are generally very stable and do not bleed/migrate and are therefore very popular for soap making as they are also very cost effective. They do however have a tendency to “clump” so they need to be mixed very thoroughly in oil before adding them to your soap base.
Micas: Generally used to provide a shimmer and shine, they are most commonly used in lipstick and eye shadows. Micas are derived from the mineral Muscovite Mica which is purified and ground into a fine, pearly translucent powder. It is then coated with dyes or pigments, or a combination of both. They produce the most stunning results in clear products, like clear melt and pour soap base, as to get the shimmery effect they need to reflect light. Unlike pigments, micas don’t tend to clump so they are easier to work with. The disadvantage of using micas in soap making is that they have a higher usage rate than both pigments and dyes. The shimmery effects are also lost in CP. As micas can be coated in dyes, some of them are not stable in CP soap and will require testing.
FAQ What do we mean when we talk about a colour bleeding/migrating?
If a colour is non-bleeding it means the colour won't migrate or bleed into surrounding areas of your soap project. An example of bleeding: You embed a red heart in a white soap base. After several days, you notice that the red heart has started to bleed (or migrate) into the surrounding white soap. The white area around the heart has now taken on a pale red colour. Over time, the red color eventually penetrates and bleeds (migrates) into all of the white soap making the edges of the embedded heart fuzzy and indistinct.
The term "bleeding" does not mean that a colour will come off onto your skin when you have a bath or shower.
FAQ What do we is mean when we say a colour is stable/unstable?
This refers to how sensitive a colour is to light, acidity or alkalinity (or pH). If a colour is sensitive to pH it will cause the colour of the soap to morph into unexpected shades when used in cold process soap. Colours that are sensitive to light will also fade in the sun, so be sure to take this into consideration (you may want to use a U.V. inhibitor).