How to Choose a Solid Shampoo Bar

Let's talk about something that has put doubt in the mind and confusion into every single person embarking on a zero waste journey: shampoo bars!

The Two Different Types of Shampoo Bars

As you all probably know, there are two different types of shampoo bars you can buy. The first one is what I like to call a "soap-based" shampoo bar, and the second one is "detergent-based" shampoo bar.

The two shampoo bars look very similar and they often share some of the same ingredients. However, they are actually very different in the way they work.

So, how do we choose? First, we need to understand a bit about pH.

Why is pH Important in Hair Care?

The first major difference between a soap-based shampoo bar and a detergen-based shampoo bar is the pH. In case you don’t know, pH is a scale used to determine if a product is acidic or basic (alkaline).

On a scale from 0 to 14, 7 is considered neutral. Vinegar, lemon or citric acid is considered acidic with a pH of 2. Whereas, something like drain cleaner will have a basic pH of 14.

Our skin is naturally acidic, in fact is often referred to as "the acidic mantle". It has a pH between 4 and 5.5.

Ph scale soap shampoo bar

Learn how to make your own shampoo bar

Soap-based Shampoo Bars

Natural, cold process soap is made using a mix of oils and sodium hydroxide, a very alkaline ingredient with a pH of 14. Since pH is always measured in an aqueous solution, oils do not have a pH.

After the saponification reaction, the sodium hydroxide used to transform oils into soap, will evaporate. This leaves a soap with a lower, but still alkaline pH, of 8-10.

Can I use a soap bar to wash my hair?

When we are using a shampoo bar made with the soap cold process method, we must finish off our shower with an acidic rinse. This acidic rise will restore the pH of our hair to an "acidic state".

If we don’t do that, our hair will feel very coarse. It will even be impossible to even run our fingers through it! Yes, we are still applying wonderful oils and butters that are amazing for our hair, but unfortunately the pH is disrupting this benefit, and sabotaging the final result.

Why can I use soap bars on my body if it's not good for my hair?

Why are we using handmade soaps on our body then? Our skin has the natural ability to restore it's acidic pH after just few minutes of using a soap bar.

Despite the high pH, your skin can truly benefit from all the goodness contained in a natural soap bar. On the contrary, our hair shaft is (chemically speaking) “dead”. It does not have the ability to restore it’s pH naturally.

Hair cuticles | How to choose a shampoo bar | Bottega Zero Waste

An alkaline product, like a soap bar, will make the cuticles (the outer part of your hair) lift and become swollen. This means your hair will be more prone to breakage and damage.  

Is any soap bar suitable for hair?

Why can we not just reduce the pH of a handmade soap bar? For example, citric acid is a pH regulator which is used to bring a formulation's pH down.

When you are making cold process soap, you are working with raw sodium hydroxide. It is the reaction of this very alkaline solution that transforms the oils into soap.

If you were to add citric acid to soap, then you effectively would “kill” some of that saponification power that comes from the alkalinity of sodium hydroxide. As a result, depending on how much citric acid you add, less oil will turn into soap and you may never achieve the saponification state. 

I have made several tests to include citric acid in soap, and the best way to go about it is by adding it after "trace". Trace is the stage in soap making after the saponification reaction has happened.

Although this does bring down the soap’s pH a little bit, you will never be able to achieve a balanced pH cold process soap bar. The reality is that handmade, cold process soap is alkaline by nature.

Detergent Based Shampoo Bars

A detergent-based shampoo bar is made using detergents called "surfactants". Surfactants stands for "surface active agents".

“Surfactants are compounds that lower the surface tension of a liquid and therefore they emulsify the grease and the dirt on our skin and help us to wash it off with the aid of water. They have a “water hating tail” (hydrophob) to catch the grease and wash it off using their “water loving” tail (hydrophil)".

(Source: Wikipedia)

Hydrophil | How to Choose a Shampoo Bar | Bottega Zero Waste

A surfactant based shampoo bar will likely have a balanced pH, between 4.5 and 6.5. The pH will depend on which ingredients have been used to make the shampoo bar.

A well formulated shampoo bar will have a balanced pH. This is because all the ingredients used, already have a low pH! 

If the formulation includes some ingredients that have a more alkaline pH, then you might see some acidic regulators such as citric acid included in the ingredients. These are used to reduce the pH to an acidic state.

A final note about soap-based and detergent based shampoo bar is that there really isn’t much difference in the ingredients used. A shampoo bar made surfactants will likely be packed with the same hair loving ingredients such as castor oil, rhassoul clay and coconut oil. 

6 Steps to Choosing a Mild, Eco-friendly Shampoo Bar

When you are looking for a detergent based shampoo bar, it's really important to read the INCI ingredient names. The INCI name (international nomenclature of cosmetic ingredients) is a standardised, and legal (in most countries), way of writing ingredients on labels so that they are understandable in every language.

Some shampoo bars will have ingredients which may be simply too aggressive for your hair. In my opinion, these are the things you need to look for in a well-balanced, eco-friendly shampoo bar:

1. Look for shampoo bars that contain a blend of surfactants

A shampoo bar using only one type of surfactant, rather than a blend, may be way too aggressive. This blend is normally obtained using surfactants with different "ionic nature" (this refers to their electrical charge) and therefore properties. 

Blending surfactants in the correct way is necessary to create a mild and well balanced product.

The 4 types of surfactants used in shampoo bars:

1 - Anionic: surfactants with a negative charge, and provide most of the cleansing properties we want in our shampoo.

In this family we find sodium cocoyl isethionate, SLS (sodium lauryl sulphate), SLES (sodium laureth sulphate), ammonium lauryl/laureth sulphate, sodium lauroyl sarcosinate, and disodium laureth sulfoccinate.

Surfactants | How to Choose a Shampoo Bar | Bottega Zero Waste

2 - Amphoteric – surfactants that have both a positive and negative charge. They are used in a shampoo formulation to thicken the shampoo, but most importantly to decrease the irritation potentially caused by the anionic surfactants.

This family includes: cocamidopropyl betaine, lauramidopropyl betaine, and cocamidopropyl oxide.

3 - Non-Ionic: surfactants with no charge. In this category we find surfactants like lauryl glucoside, decyl glucoside, coco glucoside, caprylyl/capryl glucoside.

They often have a high pH and can create a drying feeling, so are normally used in small amounts. They work mostly to provide more foaming properties when combined with other specific surfactants.

4 - Cationic: surfactants with a positive charge. These are used mostly in conditioners, or 2 in 1 shampoo and conditioners.

This is because, since our hair is negatively charged, a positive charge will effectively close the hair cuticles so it becomes less prone to damage. 

2. Choose sulfate free shampoo bars 

Sulphate surfactants, such as SLS and SLES, are known to have a more aggressive nature. Sodium coco sulfate is still derived from SLS but is a bit milder.

Sodium cocoyl isethionate is very mild but will make an even milder product when used alongside surfactants with a different ionic nature, such as cocamidropopyl betaine.

3. Go palm oil free 

If you can't avoid palm oil in a product, ask the manufacturer/brand if that palm oil is RSPO (Roundtable on Sustainable Palm Oil). Sadly, many ingredients used in shampoos (and vast majority of any other cosmetic product on the market) are derived from palm oil in some way.

Palm Oil Free | How to Choose a Shampoo Bar | Bottega Zero Waste

Palm oil is often "hidden" behind ingredients that are derived from palm oil, but carry a different name. Some palm oil derived ingredients are stearic acid, palmitic acid, cetearyl alcool, cetyl alcool, and BTMS (as part of this ingredient includes cetearyl alcool).

In some cases it is possible to find palm oil free alternatives of these ingredients. If this is the case, the brand you are buying from should state if that particular ingredient is palm oil free.

4. Avoid synthetic fragrances and colourants

Avoid anything that says “parfum”. Often, you have no way of knowing the ingredient(s) behind this generic word. I also prefer to stick to using essential oils, and would avoid using anything that contains artificial fragrances. 

Avoid synthetic fragrances | How to Choose a Shampoo Bar | Bottega Zero Waste

I really don’t see the point of using synthetic fragrances when we can use essential oils that contain hair loving properties. For example, rosemary, lavender, mint, and tea tree to name a few.

Finally, I would avoid buying any shampoo bars with bright artificial "mountain-dew-green" style colours. This will really bring no benefits to your hair and skin!

5. Make sure your shampoo bar has got plenty of good oils, butters, botanical and hair loving ingredients!

Make sure your shampoo bar contains lots of hair loving ingredients, or else it will just be a brick of surfactants.

Look, for example, for coconut oil, cocoa butter, shea butter, argan oil, avocado oil, and jojoba. Clays, such as rhassoul clay and bentonite clay, are also amazing for haircare.

Other hair loving ingredients are botanical extracts or powders (for example, nettle leaf, chamomile, aloe vera), proteins (like wheat protetin), vitamins like panthenol (Pro Vitamin B-5).

6. Look for well preserved shampoo bars 

There are many misconceptions in the green beauty industry, and preservatives are one of them. Preservatives are often doomed as “bad”. I think this is because we think of preservatives prolonging “shelf life”, and therefore going against nature.

Preservatives are actually essential to use in products that:

  • contain water

  • are going to get in contact with water

Wherever there is water, germs can form. This is especially true for water-based products (creams, liquid shampoos etc) as well as for waterless products that are used in the shower. This includes shampoo bars!

Preservatives | How to Choose a Shampoo Bar | Bottega Zero Waste

A note: shampoo bars made with soap, or soap itself, do not need preservatives. This is because their very high alkaline nature prevents bacteria from forming naturally. 

A product which contains water, or will be in contact with water constantly, but is not well preserved will expose you to a risk of infections caused by fungi, mould bacteria and other really nasty stuff.

Make sure your shampoo bar is well-preserved, using eco-preservatives, which are accepted for use in organic skincare. Some eco preservatives are benzyl alcohol, benzoic acid, sorbic acid, and dehydroacetic acid.

Also another note: preservatives are different from anti-oxidants. Anti-oxidants, such as vitamin E, grapeseed extract, rosemary extract, are used to stop oils in your formulation going rancid or to simply extend their shelf life. It does nothing to preserve your product from harmful bacteria or mould!

What do you think about shampoo bar? have you settled on a specific shampoo bar type yet? 

Have you got any questions? Let me know in the comments below!


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