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How Do You Use Surfactants in Soap Making?

Surfactants are the ingredients that make soaps, shampoos, and cleansers foam, cleanse, and remove dirt. If you’ve ever wondered how modern soap makers use surfactants to create gentle, effective products, this guide breaks it down simply.

What Is a Surfactant?

A surfactant (short for “surface active agent”) is an ingredient that reduces surface tension in water so oils and dirt can wash away. Surfactants are responsible for:

  • Cleansing

  • Lather and bubbles

  • Emulsifying oils

  • Making products mild or more powerful

Traditional cold-process or hot-process soaps use natural surfactants created through saponification.
Modern formulations often use additional surfactants to create gentler or specialty products.

Types of Surfactants Used in Soap & Cleansers

Surfactants fall into four main categories:

1. Anionic Surfactants (high cleansing, big bubbles)

Examples:

  • Sodium Lauryl Sulfate (SLS)

  • Sodium Laureth Sulfate (SLES)

  • Sodium Cocoyl Isethionate (SCI)

  • Sodium Coco Sulfate (SCS)

Best for: shampoos, face washes, body washes, syndet bars.

2. Amphoteric Surfactants (mild, helps stabilize foam)

Examples:

  • Cocamidopropyl Betaine (CAPB)

  • Lauryl Betaine

Best for: baby products, sensitive skin cleansers, balanced formulas.

3. Non-Ionic Surfactants (very gentle, low irritation)

Examples:

  • Decyl Glucoside

  • Coco Glucoside

  • Lauryl Glucoside

Best for: facial cleansers, sulfate-free products.

4. Cationic Surfactants (conditioning agents)

Examples:

  • Behentrimonium Methosulfate (BTMS)

  • Cetrimonium Chloride

Best for: conditioners, hair products — not usually used in traditional soaps.

How to Use Surfactants in Soap Making

You typically use surfactants in syndet bars, liquid soap, body wash, facial cleansers, and shampoo bars — not in traditional cold process soap.

Here’s how to do it safely and effectively:

1. Choose the Purpose of Your Soap

Your goal determines your surfactants:

Product Type Best Surfactants
Gentle face wash Coco Glucoside, CAPB
Moisturizing body wash SCI + CAPB
Sulfate-free shampoo SCI, Decyl Glucoside
Syndet bar SCI, SLSa, SCS
Deep cleaning soap SLSa, SCS

2. Calculate the Right Usage Rates

Each surfactant has a recommended percentage. Here are general ranges:

  • Primary surfactants: 20–60%

  • Secondary surfactants: 5–20%

  • Amphoteric (CAPB): 10–40%

  • Non-ionic glucosides: 4–20%

Always check your supplier’s documentation.

3. Melt or Disperse the Surfactants

Different surfactants behave differently:

Solid surfactants (SCI, SLSa, SCS):

  • Melt in a double boiler (slow, low heat)

  • Combine with other melted ingredients like butters or stearic acid

  • Mix until smooth paste forms

Tip: Wear a mask — powders are irritating to breathe in.

Liquid surfactants (CAPB, glucosides):

  • Mix into water or hydrosols

  • Combine at room temperature or warm slightly

  • Stir gently to avoid foam

4. Add Conditioning & Moisturizing Ingredients

To balance the formula, add:

  • Glycerin

  • Panthenol (Vitamin B5)

  • Aloe vera juice

  • Vegetable oils (in small amounts)

  • Butters

  • Hydrolyzed proteins

These help counteract the drying effect of strong surfactants.

5. Adjust the pH

Unlike cold-process soap, surfactant-based products must have a controlled pH:

  • Facial products: pH 4.5–6

  • Body washes: pH 5–6.5

  • Shampoo bars: pH 5–6

  • Syndet bars: pH 5–7

Use citric acid or lactic acid to lower pH.
Use sodium hydroxide solution to raise pH (carefully).

6. Add fragrances, essential oils, and preservatives

Fragrance or essential oil:

Usually 0.5–3% depending on safety guidelines.

Preservatives:

A must for any product containing water.
Use things like:

  • Optiphen

  • Germaben II

  • Liquid Germall Plus

Check usage rate (usually 0.5–1%).

7. Pour or Mold the Final Product

Depending on what you’re making:

  • Liquid soaps: pour into bottles

  • Syndet bars: press into molds and let harden

  • Shampoo bars: cool and cure 24–72 hours

  • Face wash: package in pump or squeeze bottles

No long cure time is needed like with cold process soap.

Example Formula (Simple Syndet Bar)

Here is a beginner-friendly base:

  • 50% Sodium Cocoyl Isethionate (SCI)

  • 20% Cocamidopropyl Betaine (CAPB)

  • 10% Cocoa butter

  • 10% Stearic acid

  • 5% Vegetable glycerin

  • 3% Essential oil

  • 2% Preservative (if needed)

This gives you a gentle, bubbly bar that works for most skin types.

Final Tips for Using Surfactants

  • Wear gloves and a mask when handling powders

  • Avoid overheating SCI — it burns easily

  • Test pH carefully before bottling

  • Keep formulas balanced (too much surfactant = drying)

  • Start small and tweak as needed