How to Choose a Solid Shampoo Bar

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Let's talk about something that has set some doubts and confusion into every person embarking on a zero waste journey: shampoo bars!

The difference between shampoo bars

As you all probably know, there are two different types of shampoo bars available to purchase.

The first one is what I like to call a "soap-based" shampoo bar, and the second one is "detergent based" shampoo bar.

They look very similar and they often share some of the same ingredients but they are actually very different in the way they work. So, how do we choose?

shampoo bar

Talking about pH: why is it important in hair care?

The first major point of difference is the pH. In case you don’t know, pH is a scale used to determine if a product is acidic or basic. On a scale from 0 to 14, 7 is considered neutral. Vinegar, lemon or citric acid is instead acidic with a ph of 2, while 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" with a pH between 4 and 5.5.

Ph scale soap 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 leaving the soap with a lower but still alkaline pH of 8-10.

When we are using a shampoo bar made with the soap cold process method, we must finish off our shower with an acidic rinse to bring that pH of our hair back to an "acidic state". If we don’t do that, our hair will feel very coarse, it will be impossible to even run our fingers through them. Yes, we are still applying wonderful oils and butters that are amazing to our hair, but unfortunately the pH is disrupting this benefit and taking over in the final results.

Why are we using handmade soaps on our body then? Our skin has the natural ability of restoring 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 natural goodness contained in a natural soap bar. On the contrary, our hair shaft is - chemically speaking - “dead” and does not have the ability to restore it’s pH naturally.

An alkaline (high pH) product 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. 

hair cuticles

Why can we just not do something to bring the ph of a handmade soap down? 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 is given by the alkalinity of sodium hydroxide. As a result, depending on how much citric acid you put, less and less portion of oil will turn into soap and you might actually never achieve the saponification state. 

I have made several test to include citric acid in soap, and the best way to go about is by adding it after "trace", which is the stage soap hits 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 slightly alkaline and this is its very nature.

Detergent Based Shampoo Bars

A detergent-based shampoo bar is made with detergents  called "surfactants", a name that 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)". (definition from Wikipedia)

surfactants hair care shampoo bars

A surfactant based shampoo bar will likely have a balanced pH between 4.5 and 6.5 and this depends on which ingredients have been chosen to make the shampoo bar. A well formulated shampoo bar will have a balanced pH because the ingredients used already have a low pH! If the formulation includes some ingredients that have a more alkaline ph, then you might see acidic regulators such as citric acid included in the ingredients, used to bring the ph down to an acidic state.

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


shampoo bar

6 easy 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 name of the ingredients. 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. 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 1 type of surfactant only, 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.

There are 4 types of surfactants:

1 - Anionic: they have 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, disodium laureth sulfoccinate.

Amphoteric – they have both a positive and negative charge. They are used in a shampoo formulation to thicken up the shampoo but most importantly to decrease the irritation potential of the anionic surfactants. We have here for example: cocamidopropyl betaine, lauramidopropyl betaine, cocamidopropyl oxide.

3 - Non-Ionic: they have 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 give a drying feeling, so these are normally used in formulations in small amounts. They work mostly to provide more foaming properties when combined with other specific surfactants.

4 - Cationic: they have a positive charge, and are used mostly in conditioners or 2-1 shampoo/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 a bit milder. Sodium cocoyl isethionate is very mild but will make an even much milder product when used along surfactants with a different ionic nature such as cocamidropopyl betaine.

3. Go palm oil free 

If you can't avoid the palm oil from 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 is often "hidden" behind ingredients which is derived from palm oil, but carry a different name. Some palm oil derived ingredients are stearic acid, palmitic acid, cetearyl alcool, cetyl alcool, BTMS (as part of this ingredient includes cetearyl alcool). In some cases it is possible to find palm oil free alternatives of these same ingredients. If this is the case, the brand you are buying from should state if that particular ingredient is palm oil free.

Shampoo bar

4. Avoid synthetic fragrances and colourants

Avoid anything that says “parfum” as you often 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 is using artificial fragrances. 

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

Finally, I would avoid buying any shampoo bars with bright artificial "mountain-dew-green" style colours as 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 has hair loving ingredients as part of the formulation or else it will just be a brick of surfactants. Look, for example, for coconut oil, cocoa butter, shea butter, argan oil, avocado oil, 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).

shampoo bar botanical extracts

6. Look for well preserved shampoo bars 

I often see many misconceptions in the green beauty industry and one of these is around preservatives. Preservatives are often doomed as “bad” and I think this is because we are brought to think of preservatives like something that is there to prolong “shelf life” and therefore going against nature. But preservatives are actually essential to use in products that:

  • contain water

  • are going to get in contact with water

Whenever there is water, germs can form. This is especially true for water based products (creams, liquid shampoos etc) as well as for waterless products which are using in the shower – yup, shampoo bars! A note: shampoo bars made with soap (or soap itself) do not need preservative because their very high alkaline nature prevents bacteria to form naturally. 

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

So, 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, dehydroacetic acid.

Also another note: preservatives are different from anti-oxidant. Anti-oxidants, such as Vitamin E, grapeseed extract, rosemary extract, are used to avoid oils in your formulation to become 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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