Shampoo bars have gained popularity as an eco-friendly alternative to liquid shampoos, but not all shampoo bars are created equally. There are two main types of shampoo bars: cold process soap-based bars, which are basically soap, and syndet bars. Understanding the differences between these two can help you choose the right option for your hair care needs.
Cold Process Shampoo Bars

Cold process shampoo bars are made using traditional soap-making methods, combining oils and lye through saponification. These bars are typically formulated with specific ingredients like castor oil and butters to benefit the hair and produce a good lather. They are basically just soap and because of the alkalinity of the ingredients, these bars have a high pH of around 9 – 10, which is harsh on your hair, as the optimal pH for you hair is 4.5 to 5.5. This high pH can damage your hair in a number of ways:
- Increased frizz and static by increasing the negative electrical charge on your hair fibres causing them to repel each other and create frizz, resulting in more tangles and breakage.
- An alkaline pH causes the hair cuticles to lift and open up, making the hair shaft more vulnerable to damage because it will be more porous and less elastic, so more prone to breaking.
- Open cuticles allow moisture to escape from the hair shaft making it dry and brittle and also resulting in colour fading.
- Products with a pH higher than 5.5 can disrupt the scalp’s natural protective barrier, leading to dryness, itching and other issues. It can also promote growth of bacteria leading to dandruff and dermatitis.
- With these bars you would need to use an acidic rinse to lower the pH. This however, will still not introduce any conditioning properties to your wash.
These bars are cheaper to make but wash away quicker and are not kind to your hair.
Syndet Bars

Syndet bars, short for “synthetic detergent” are basically a solid version of shampoo. These are the types of bars you see sold in Lush and health food shops. The bars use mild surfactants (foaming agents) instead of soap and have lots of great features:
- They are pH balanced, with a lower pH of usually around 4.5 – 6, which is much better for the health of your hair.
- No need for an acidic rinse.
- Work well in hard water, unlike cold process soap.
- Gentler cleansing with conditioning properties to soften, smooth and moisturise your hair.
- Economical – one 55g bar can last up to 80 washes.
- You can alter the recipes to suit your hair type and climate and you can add in lots of lovely nourishing and conditioning ingredients, from oils and butters to plant extracts and essential oils.
- Kind to the environment as the bars need no packaging.
- Quick and simple to make once you know how and ideal for travelling as they are compact with no risk of spills or leaks.
If you are interested in finding out more about shampoo bars, and how to make them, then check out my course – Master the Art of Creating Luxurious Shampoo Bars