The way you incorporate color into your soap depends on the kind of soap and the kind of colorant you’re using. You can color the soap directly by adding the colorant to the soap mixture. You can also add pieces of colored soap as in the “chunking” and confetti techniques. Here, we’ll talk about how to use color in each of the soapmaking techniques.
Coloring Cold-Process Soap
When you’re working with cold-process soap, a number of colorants will fade, change, or disappear altogether due to their reaction to active lye. Natural plant dyes will be obliterated except for a few tenacious examples. Certain food colorants will change color entirely.
Fortunately, there are also many kinds of colors that will hold up through the rigors of the cold-process method. A few plant dyes, including some spices, produce colors ranging from subtle to bright. Ultramarines and oxides hold up very well, as do many micas.
Coloring Hot-Process Soap
In the hot-process techniques, you can add color after the soap is neutral, so you have more choices available than in cold process. You can often use less colorant, with more predictable results.
Getting colorants distributed evenly in hot-process soap is difficult. When you add color at the end of the cooking period, you are trying to add it to a very thick, sticky mixture. Some of the soap has cooled into tiny lumps, while some of it is fluid enough to accept the colorants.
Experiment with different ways of incorporating color into hot process. One thing to try is to remove a small portion of the mass you want to color, mix the colorant into that, and then mix the colored portion back into the rest. Give it, and yourself, a good workout trying to get the color evenly distributed.
In hot processing, and in fact all lye soapmaking techniques, you can add some color elements from the beginning of the process. You may use an infusion of an herb to mix with the lye, or you may use an oil that has been colored with herbs. These herbal infusions will usually take quite a beating in the process, but there are herbal colorants that transmit well this way.
Colors in Hot and Cold
With hot process, if the soap is still slightly alkaline, colorants that fade in alkaline soap will do the same here. Chances are about fifty-fifty that a colorant said not to be stable in cold process will be stable in hot.
You can also add mineral pigments to the early stages of making lye soap. Ultramarines and oxides perform beautifully when added with the lye to the water to make a tinted lye solution. Keep in mind that the entire batch will be that color. You can make two separate batches simultaneously using color in this way, and swirl them together, avoiding the complication of adding colorant later. You can also vary the color at the end with more colorant, or pieces of differently colored soap. Planning ahead pays off.
Coloring Casting Soap
Soap casting is where color really takes center stage. The premade soap base will accept just about any pigment. Herbs will eventually turn brown in any soap, but in soap casting, they’ll keep their color for a little while.
You can use different kinds of coloring together in the same projects. Combining liquid soap dye with a little mica makes a very simple and beautiful soapcasting project. Ultramarines and plant materials can be used together to great effect. Again, imagination is the key.
It doesn’t take much pigment for transparent soap to go from clear to opaque, or so saturated with color that little light goes through. Often, less is more. Take advantage of the beauty of the way light passes through the soap, especially with mica.
Enjoying Natural Color Sources
Nature provides us with beautiful colors that can be applied to coloring soap. You can add plant material directly to the soap mixture to create not only color but texture as well. Most plant material that starts out green will eventually turn brown. However, some botanicals–calendula petals, for example–retain their color when added at the end of the process. You can also use dried herbs in hand-milling products if you really want the color to stay for a while. Be sure that when you’re adding herbal ingredients directly into the soap, you remove sticks, twigs, and other sharp parts of the plant.
Highly sensitive individuals should avoid plants with lots of volatile oils such as rosemary, the mints, and even lavender. Look to herbal reference books for sensitivity information and remember that it is always wise to err on the side of caution.
To get the color from the plant matter into your soap, you can use a variety of methods. Infusing oil and water with a high concentration of the color herb creates a usable dye. Be sure to record the amounts, temperatures, and length of infusion time so you can repeat what works. There are a few commercially available plant dyes.
There are quite a few plants that work as colorants for soap, but annatto seed and alkanet root are some of the most easily used. Since plants vary from season to season and crop to crop, you should test each new supply you purchase.
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Excerpted from DIY Artisanal Soaps: Make Your Own Custom, Handcrafted Soaps! by Alicia Grosso. Copyright © 2016 Adams Media, a division of Simon and Schuster, Inc. Used by permission of the publisher. All rights reserved. Interior images © iStockphoto.com.