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Soap-based vs Soap-free Shampoo Bars

Updated: Jul 12, 2022

If you're planning to make the switch to a solid shampoo bar, it's important to know that not all shampoo bars are the same (but I'll save you some time and just tell you that it's the soap-free bar that you want!)

Each person’s hair is different, texture and thickness can vary dramatically and one bar won’t fit all which is why it took me such a long time to develop a range of shampoo bars! I thought sharing some of what I've learned along the way might help if you're thinking about making the switch to a solid shampoo bar.

It's all about the pH! Our scalp is an acidic environment with a pH level between 4.5 - 5.5 and needs a pH-balanced product to maintain optimum pH levels. Soap-free shampoo bars are pH balanced and have pH levels between 4 – 6 (ideal for hair & scalp), while soap-based bars have a naturally high pH of 9-10.

Hair strands are made up of many different layers. The cuticle is the outermost layer of the hair, that shields and protects the inner part of the strand from damage, but it wears away over time due to UV (sun), chemical (hair dye/products), heat (straightening/curling) and mechanical (brushing) damage, and once it’s gone, it cannot be repaired. The appearance and strength of our hair are determined by the condition of the cuticle, so we really want to take care of it!

To maintain healthy hair and scalp we need our hair cuticles to lie flat. High pH product like soap, can leave the cuticles open which results in friction, tangling, and even damage over time as they rub against each other. Open cuticles also reduce shine and make the hair appear dull. Soap-free (pH balanced) bars have scalp-friendly pH which helps cuticles to lie flat resulting in healthy-looking and shiny hair.

Beware of soap masquerading as shampoo - soap-based shampoo bars are technically soap!

They tend to contain more nourishing oils and plant butters than hand & body soaps, but if you consider their chemistry, these bars are soap. Soap is made by the saponification process, when lye solution (sodium hydroxide + water) interacts with fatty acids such as oils and butters (or even lard!) and results in soap.

So why is it so bad for your hair? Soap has a high pH which makes it alkaline and using an alkaline product on our acidic hair will change the chemistry of the hair and cause damage. Using soap to wash your hair will strip fatty acids from the hair cuticle, even removing the cuticle in some instances, and allowing water to enter the hair shaft which then causes friction, matting, tangles, and static, fly-away hair. It can also leave a residue that builds up on your hair, making it feel lank and matted. The typical advice if this happens is to use a cider apple vinegar rinse to make the hair look and feel better. The theory appears to be that the vinegar will return your hair to an acidic pH after using the alkaline soap and, although it might remove the waxy or soapy residue from the hair, it can’t replace the lost fatty acids or repair the damaged cuticle. Nothing in the chemical structure of vinegar that will help it bind to your hair, so it will just simply wash off. (Hope the smell does too!)

Soap-free shampoo bars don't undergo a saponification process, therefore are truly soap-free. They are made using surfactants, conditioners, and hair-loving ingredients, such as nourishing oils, clays and botanicals.

Surfactants are substances that help oil and water mix by binding with the oily, dirty stuff in your hair when you lather, and then bind with water when you rinse, washing away all the grime and leaving you with fresh, clean hair. This is how a liquid shampoo works and how I have chosen to make my solid shampoo bars.

I know that word ‘surfactant’ can make some cringe, but not all surfactants are made equal. SLS (Sodium lauryl sulphate) although commonly found in commercial shampoos strips oil from the hair and is best to be avoided. If you would like to go completely sulphate-free, then you should also avoid: SLES (sodium laureth sulphate) and SCS (Sodium coco sulphate). I avoided all of these ingredients in my shampoo bars and chose instead the milder, coconut - derived Sodium Cocoyl Isethionate which is a biodegradable and a sustainable option. It creates a rich lather to gently lift away dirt and grime. It's sometimes referred to as 'baby foam' which makes it a great option for sensitive scalps too.

Of course, there will be people who can quite happily use soap as shampoo, particularly those with fine hair which has fewer layers of cuticle, or short hair that is cut frequently. But for anyone who has never tried a solid shampoo, or perhaps had a miserable experience with a shampoo bar previously I hope this read has been helpful and that you might consider giving a soap-free shampoo bar a go.

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Oct 10, 2023
Rated 5 out of 5 stars.

Really informative - thank you!


Mar 14, 2023
Rated 5 out of 5 stars.

Thank you, such an informative article which explains why I've struggled with other shampoo bars and had no problem switching to yours!

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