Cold Process Soap — Part 2: Additives

Cold process soap additives including oatmeal, clay, charcoal, turmeric, botanicals, and handmade soap bars arranged on a warm stone surface.

Written by Elizabeth Mika
Founder and Maker, Bramble & Bear™ Soap Co.

What honey, oatmeal, clay, milk, charcoal, and other soap additives actually do

Cold process soap starts with a simple foundation: oils, water, and sodium hydroxide.¹

Cold process soap additives are ingredients used in relatively small amounts to change a bar’s lather, hardness, feel, color, texture, or appearance.

From honey and colloidal oatmeal to clay, milk, charcoal, salt, and sodium lactate, different additives serve very different purposes.

Some have a practical job. Others add botanical character or help create a certain look.

Here are some of the most common additives you may see in handmade soap—and what they actually do.

Additives That Change Performance

These can change hardness, lather, slip, or how the soap behaves in use.

The visual below summarizes common cold process soap additives that can affect hardness, lather, slip, and creaminess. A complete text version follows the image.

Additives That Change Performance - Text Version

Salt

A little salt can help create a firmer bar.

In much larger amounts, salt is used to make specialty salt bars, which behave differently from ordinary cold process soap.

Sodium Lactate

Sodium lactate helps fresh soap harden, making it easier for the soapmaker to remove from the mold and cut.

Despite the name, lactate does not mean the soap contains milk.

Sodium Citrate

Sodium citrate helps bind some of the minerals found in hard water.

This can help reduce the film commonly called soap scum.

Tussah Silk

Tussah silk is used in very small amounts by some soapmakers to create a smoother, silkier-feeling lather.

Beer, Sugar & Honey

Beer, sugar, and honey provide sugars that can help cold process soap produce more bubbles.

Honey can also deepen the color of a finished bar.

Milk

Goat milk, cow milk, coconut milk, and other milks contribute sugars and, depending on the milk, fats that can influence the character of the finished bar and its lather.

Botanical & Skin-Feel Additives

These are often used for texture, feel, or botanical character.

The visual below summarizes several botanical and skin-feel additives used in cold process soap and what they can contribute to the finished bar. A complete text version follows the image.

Botanical soap additive comparison showing colloidal oatmeal, aloe vera, calendula, chamomile and green tea and how they contribute texture, skin feel or botanical character, beside soap, oats and botanicals.

Botanical & Skin-Feel Additives - Text Version

Colloidal Oatmeal

Colloidal oatmeal is oat material processed into very fine particles.

In soap, it can give the bar and lather a soft, silky feel, which helps explain why oatmeal soap remains so popular.

In cold process soap, colloidal oatmeal is incorporated into the finished bar as part of the overall formulation, where it can contribute to the bar’s texture and the soft, silky character of the lather.

Colloidal oatmeal also has recognized uses in certain skin-protectant products, although those products are formulated and regulated differently from soap.²

What About Herbs & Botanical Extracts?

Aloe, calendula, chamomile, green tea, and other botanicals can add botanical character to handmade soap.

Cold process soap also goes through saponification—the chemical reaction that transforms oils and sodium hydroxide into soap.

The role of a botanical ingredient in finished soap depends on how it is incorporated into the formula and how it behaves during the soapmaking process.

Color & Texture Additives

Some additives are used mainly to create natural-looking color, texture, slip, or visual interest.

The visual below summarizes several additives used to create color, texture, slip, or visual interest in cold process soap. A complete text version follows the image.

Soap color and texture additive comparison showing kaolin clay, French green clay, rose clay, indigo, turmeric and activated charcoal with their typical color effects and uses, beside colored soaps and clay dishes.

Color & Texture Additives - Text Version

Clays

Clays such as kaolin, rose clay, and French green clay can contribute color, texture, and slip.

Clays are also used in cosmetic products for a variety of purposes. In cold process soap, however, those broader cosmetic claims should not automatically be applied to the finished bar.³

Activated Charcoal

Activated charcoal is especially useful for creating dramatic black and gray soap.

Activated charcoal is also used in cosmetics for a variety of purposes, but those broader claims do not automatically apply to cold process soap.³

How Additives Contribute to Soap

Honey, oatmeal, clay, milk, silk, and botanical extracts can contribute to characteristics such as lather, texture, color, slip, and the overall character of a finished bar.

Some of these ingredients are also used in cosmetic or drug products for other purposes. Under U.S. regulations, however, a product marketed as traditional soap must be represented only for cleansing. Cosmetic claims such as moisturizing or skin softening can cause the product to be regulated as a cosmetic, while therapeutic or disease-related claims can cause it to be regulated as a drug.³

The contribution of an additive also depends on the complete formula, the amount used, and the soapmaking process.

A Note About Ingredient Claims

Under the FDA regulatory framework, traditional soap is represented for cleansing. Claims such as moisturizing or skin softening can place a product in the cosmetic category, while claims to treat or prevent disease or affect the structure or function of the body can place it in the drug category.³

Bramble & Bear™ soaps are marketed for cleansing only. References to ingredients and their formulation roles in this article are educational and are not intended as cosmetic, therapeutic, or drug claims.

Explore Bramble & Bear Cold Process Soap

Discover our collection of handmade cold process soap, thoughtfully formulated with oils, butters, and other ingredients chosen to work together in the finished bar.
Shop Handmade Soap →

Previous in the series:
← Cold Process Soap — Part 1: Oils

Next in the series:
Cold Process Soap — Part 3: Fragrance & IFRA →

Sources

1. U.S. Food & Drug Administration, Frequently Asked Questions on Soap. FDA explains the regulatory definition of traditional soap and describes soap as being formed when fats or oils react with an alkali such as lye.

2. U.S. Food & Drug Administration, OTC Monograph M016: Skin Protectant Drug Products for OTC Human Use. Colloidal oatmeal is recognized as an active ingredient in certain OTC skin-protectant products when those products meet the applicable formulation and labeling requirements. That does not mean every soap containing colloidal oatmeal is a skin-protectant drug or provides the same effects.

3. U.S. Food & Drug Administration, Cosmetics Labeling Claims and Is It a Cosmetic, a Drug, or Both? (Or Is It Soap?). Claims that a product treats or prevents disease or affects the structure or function of the body can change how the product is regulated.