Shampoo Bars: The Different Types & How They Work

We wash our hair to remove sebum, sweat, and hair care products that build up on our hair strands and scalp and make our hair look, feel, and smell less than fresh! Liquid shampoo is typically a blend of water (around 80%), conditioning agents, fragrance, colours, thickeners, preservatives, and most importantly, surfactants. 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.

Your 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!

Did you know that your hair has a pH value? Individual pH values will vary, but it usually falls between 4 and 6 (acidic), with virgin hair having a pH of 3.7. A good shampoo is pH balanced and won’t alter the acidic pH of your hair.

Beware of soap masquerading as shampoo!  There are two different types of shampoo bars on the market – one type is made with a solid surfactant as a base, and the other type is a natural cold process soap. Confusingly, they are both called and marketed as shampoo bars, but only the one made with surfactants is technically shampoo! These two types of bars may look similar, but they aren’t the same at all. As we saw above, surfactant-based shampoo is typically acidic and, therefore, pH balanced for the hair. However, natural soap has a pH of around 9 (alkaline), which is not ideal at all! Please note that we are in fact huge fans of natural soap and think it’s a perfect swap for liquid hand soaps and body wash 🖤

So why is it so bad for your hair? Using an alkaline product on our acidic hair will change the chemistry of the hair and cause damage… permanent damage that cannot be reversed. 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. This makes it swell and causes friction, matting, tangles, and static, fly-away hair. “The soap, which is also an anionic detergent, in contact with water, leaves an alkaline residue that is very harmful to the hair and skin and that precipitates in the form of calcium salts which accumulate in the hair strands, leaving them opaque and tangled.” (Ref). So, basically, soap can also leave a residue that builds up on your hair, leaving it feeling lank and matted. No thanks!

Hair with an alkaline pH is also not good if you colour your hair. “Hair with a very alkaline, porous structure will not retain colour effectively. In this instance, the cuticle will fail to hold the new pigments, which will ultimately rinse out prematurely.” (Ref)

Have you ever been advised to do an acid or vinegar rinse after using a shampoo bar? This is typically the advice given when the bar you are using is soap. The theory here is that the vinegar will return your hair to an acidic pH after using the alkaline soap. It might remove the waxy or soapy residue on the hair; however, it can’t replace the lost fatty acids or repair the damaged cuticle. There’s nothing in the chemical structure of the vinegar that will help it bind to your hair, so it will just simply wash off.

As a very general guide here are some of the ingredients to look out for:

Shampoo: there are many different surfactants in shampoo bars, but some of the most common ones will be Sodium Lauryl Sulfate (SLS), Sodium Laureth Sulfate (SLES), Sodium Coco-Sulfate (SCS), Sodium Cocoyl Isethionate (SCI), Sodium Lauryl Sulfoacetate (SLSa). There might also be a secondary surfactant present, such as cocamidopropyl betaine or disodium cocoamphodiacetate.

Soap: this will be a blend of saponified plant oils and butters, and the ingredients label will have names such as Sodium Cocoate (coconut oil), Sodium Olivate (olive oil), Sodium Sunflowerate (sunflower oil), Sodium Shea Butterate (shea butter), Sodium Castorate (castor oil). These bars will also contain water (aqua) and glycerine on the ingredients list.

If you aren’t sure if you have shampoo or soap, you can send us a list of the ingredients, and we can try and help you work it out!

It’s worth noting that the issues you can get with using an alkaline soap on your hair – waxy build-up, dryness, etc. – can also happen with some (poorly formulated) shampoo bars. That is because some of the surfactants listed above have an alkaline pH, such as SCS, SLS, and SLES. The difference is that surfactants based shampoo bars can have their pH altered by the addition of certain substances such as citric acid or lactic acid. A well-formulated bar will likely be around pH 5, and a bar made with SCI or SLSa will already have an acidic pH. The pH of cold process soap cannot be altered – it is just not possible. We’ve seen soap bars for sale that have had apple cider vinegar added to them, and they’re being marketed as ‘2-in-1 shampoo and conditioner’ bars, but vinegar is too weak an acid to make a difference here against a very strong alkali. Even if a strong acid was added, it wouldn’t work - you simply cannot reduce the pH of soap and still have it remain soap.

- You only really need to apply shampoo to your scalp and the roots of your hair – the ends are the most fragile part of the hair and typically don’t get very dirty anyway.

- Wet your hair and the shampoo bar and then either rub the bar on to your scalp and roots or rub the bar between your hands to create a lather (or do a combination of both), then use your fingers to massage the shampoo into a lather as you would when using liquid shampoo.

- Let your shampoo bar dry out in between uses – use a draining soap dish and don’t let it sit in a pool of water, to ensure it lasts longer and doesn’t turn soft and dissolve.

- You don’t need to do an acidic rinse, but you may need a conditioner, especially if you have dry, long, frizzy, or curly hair to prevent tangles and breakage.

- You might have a transition period while you get used to the shampoo bar, but it shouldn’t last more than a few washes. We have found that with a well-formulated shampoo bar, it is entirely possible to have no transition period.

Of course, having said all that, there will be people who can quite happily use soap as shampoo, and it works well for them, particularly people with have fine hair with fewer layers of cuticle or short hair that is cut frequently. So if that is you and you love your soap-based shampoo, stick with it - you do you! But for those people out there that have had one miserable experience after another with shampoo bars, we hope this has been some help and that it will make choosing a shampoo in the future a little less painful.

You can see the selection of shampoo bars we have in stock here on our website.

Please drop us a message if you have any questions about shampoo bars, and we will do our best to help!

🖤 Jacqui & Nicky