How to Make a Gentle Shampoo Bar

This sulphate-free shampoo bar recipe is built around Sodium Cocoyl Isethionate, one of the mildest surfactants available for solid haircare. Whether you're developing a shampoo bar to sell or simply want to know exactly what's going on your scalp, this formula is a solid place to start.

The result is a bar that lathers well, rinses clean, and leaves hair feeling conditioned rather than stripped. We've kept it fragrance-free so it works as a finished product for sensitive scalps, but also so you have a clean, stable base to build from if you want to add your own scent or actives.

THE FULL PROCESS

Weigh out all ingredients separately before you begin.

Add the Sodium Cocoyl Isethionate Powder to a large mixing bowl (or stand mixer bowl for batches larger than 5 bars). Set aside.

In a saucepan, combine the Cetyl Alcohol, BTMS-25, and Stearic Acid.

Melt gently over a medium-low heat, stirring occasionally, until the mixture is clear and runny. Then add the Cocamidopropyl Betaine, Sodium Citrate, Citric Acid, and Cationic Guar Gum Powder to the melted wax phase. Stir until fully combined and dissolved. The mixture will become more opaque and noticeably thicker.

While still warm, pour the mixture directly over the SCI Powder.

Stand mixer: Use the flat beater attachment and mix until a smooth, pressable dough forms. By hand: Use a spatula to press and fold the mixture against the sides of the bowl until the same dough-like consistency is reached.

Line your mould cavities with cling film. For this demonstration we used a simple, two-part 3d printed compression mould, designed and printed in-house.

Portion the dough by weight to match each cavity, press in firmly, then fold the cling film over the top and press again to compact.

De-mould after pressing, use the cling film to ease the bar out cleanly, and set on a rack to dry and harden for a minimum of 12 hours before use or packaging.

NOTES

Understanding Shampoo Bar Dilution

A core concept to understand when formulating shampoo bars is that the ingredients we use are diluted upon use. While our shampoo bar formulation may include 53.80% Sodium Cocoyl Isethionate, that’s much more concentrated than what the hair actually experiences. When used in the shower or bath, a shampoo bar is diluted by the water present. Furthermore, this dilution doesn’t only apply to the surfactant, but to all present ingredients within the formulation. This is an important factor to remember, especially if you desire certain active inclusion rates for raw materials. We wanted to better understand the true dilution for a shampoo bar. As such we conducted our own in-house testing and discovered a dilution ratio of 1:3.1 (3.1 parts water to 1 part shampoo bar delivered). So when adjusting or assessing the effect a shampoo bar may have when actually used on hair, consider this dilution ratio. Within the context of our 53.80% Sodium Cocoyl Isethionate, the resulting active concentration upon use would be approximately ~13%.

How to Control pH in a Shampoo Bar

One of the key things about this shampoo bar recipe is the ability to control our pH, something that has a massive impact on the end result of the hair. The Sodium Citrate and Citric Acid work together as a pH buffer at 2% of the bar formulation. The buffer makes our pH control more stable than simply using citric acid alone to bring down the pH. Our desired pH range for this bar is between 4.5-5.5 which is widely considered to be the ideal range for healthy hair. You can tailor the ratio of Citric Acid and Sodium Citrate in your buffer should you desire a different pH. From our testing, with the current ratios in our recipe’s pH buffer we achieved a pH of 4.81 which is within our ideal range.

How to Add a Fragrance in a Shampoo Bar

While we have left out fragrances from this bar, should you want to add in a desired fragrance this bar provides a strong foundational base. Your fragrance use must be IFRA compliant and within their limits. IFRA set limits based on categories, this shampoo bar is IFRA Category 9 (rinse-off products with body/hand exposure). Check the IFRA certificate from your chosen fragrance supplier and find the maximum % for Category 9, that will be the maximum fragrance inclusion rate for you to remain IFRA compliant. While developing this formula we first tested with fragrances included at 2%, which worked well for the fragrance we were using. After adding your fragrance, remember to rebalance and adjust your pH buffer ratios to achieve your desired pH. You do this by adjusting the amount of Citric Acid and Sodium Citrate.

FREQUENTLY ASKED QUESTIONS