Shampoo Bars using Surfactants vs. Cold Process Soap Method. What’s the Difference?

If you’ve made the switch to shampoo bars—or are thinking about it—you’ve probably noticed there are two main types: ones made with surfactants and ones made using the cold process soap method. While they may look similar, they behave quite differently on your hair. So which one is better? 

Surfactant-Based Shampoo Bars

Surfactants are cleansing agents often derived from coconut or other natural sources. Think of them as the gentler, solid version of what’s in your liquid shampoo without the bottle and with a cleaner ingredients list.

✅ Pros:

• pH balanced for your scalp – Surfactant-based bars are formulated to match the natural pH of your hair and scalp (around 4.5–5.5), so they won’t disrupt the moisture barrier or cause dryness.
• No transition period – Since they behave like liquid shampoo, there’s no “adjustment” phase like you might experience with soap-based bars.
• Customizable – These bars can be enriched with conditioning agents, proteins, and botanical extracts to suit different hair types.
• Works well with hard water – Less risk of buildup or that “waxy” feeling some soap bars leave behind.

❌ Cons:

• More complex to make – They require precise formulations and a bit more ingredient knowledge.
• Not strictly natural – Even though many surfactants are derived from natural sources, they’re still considered more processed than traditional oils and lye.

Cold Process Soap Shampoo Bars

Cold process shampoo bars are essentially bar soaps. They cleanse with the natural power of saponified oils like coconut, olive, castor, and shea butter.

✅ Pros:

• Made with simple, natural ingredients – Just oils, lye, and maybe some essential oils or botanicals.
• Eco-friendly and easy to make – Great for beginners in soap making who want an all-in-one bar for hair and body.
• Long-lasting – These bars are super firm and can last a long time if stored properly.

❌ Cons:

• High pH (alkaline) – Traditional soap has a pH around 8–10, which can raise the hair cuticle, leading to dryness or frizz for some people.
• Not ideal for any hair type – Especially if you colour your hair or have fine, dry, or curly hair, soap-based shampoo might be too harsh.
• Requires an acid rinse – To rebalance pH and smooth the hair cuticles that have lifted due to the high alkalinity.  This is also a temporary fix. 

Which Should You Choose?

If you want a gentle, salon-like cleanse without the plastic bottle, surfactant-based bars are your best bet for all types of hair.

On a personal note, I tried a cold process soap on my hair, and it left my hair dry and brittle.  I had to grow out my damaged hair. However, I do have many clients who swear by cold process soap as a shampoo.  So if you do want to try cold process bars, know the consequences can be final and be sure to "repair" your hair with an acid rinse.

When it comes to shampoo bars, the real story should be which shampoo bar is best for your hair and scalp?