Understanding pH & Bar Soap

Bar soap’s pH is one of the most popular topics that we cover in bar soap development. Here, we break down what pH is and why it matters so much for bar soap users.

What is pH?

pH is a measurement of the hydrogen ion concentration in an aqueous solution – pH stands for ‘potential of Hydrogen.’ In chemistry, it is a scale used to specify how acidic or alkaline a water-based solution is.

pH diagramNeutral is a pH of 7, and anything below that level is acidic, and anything higher than that is alkaline.

pH values of common substances:  
Battery Acid: 0
Lemon Juice: 2.0
Black Coffee: 4.5
Milk: 6.6
Blood: 7.34 – 7.45
Bleach: 12.3


Bar Soap & pH

Generally, extruded soap, like the kind that we manufacture at our Winooski, VT factory, has a pH range of 8.0 – 10.0 depending on its INCI.

It’s critical to note that while it is an important characteristic of a skincare item, pH does not have a direct relationship to how harsh or mild a product is.

The Acid Mantle

The skin has a barrier that is referred to as the acid mantle, which is a very thin, slightly acidic film on the surface of the skin that acts as a barrier to bacteria, viruses, environmental pollutants, and other potential contaminants. A healthy acid mantle is made up of lipids, including ceramides and free fatty acids, which help to maintain the optimal amount of healthy bacteria and flora for skin to remain healthy, balanced, and protected. The acid mantle can have a pH between 4.5 and 6.2, depending on factors such as age, gender, ethnicity, climate, and body part.

Short term exposure to a slightly acidic or alkaline material, such as bar soap, does not harm the acid mantle. Healthy skin can rebalance its acid mantle in a matter of minutes, and it is long-term or prolonged exposure to a high pH product, such as a lotion or other leave-on product, that can cause damage and negatively affect the acid mantle.

Even if no soap is used to wash the skin, tap water alone will slightly impact the pH of the acid mantle. Other skincare applications, such as excessive chemical exfoliation with an AHA or BHA, are much more likely to have a negative effect on the acid mantle and reduce overall skin health.

Testing Bar Soap pH

It is also important to remember that pH is designed to measure a value in a water-based solution – bar soap is a nearly solid material, so when testing it, it needs to be dissolved in water to get an accurate reading.

If you have additional questions about bar soap pH and how it impacts that products that we manufacturer for our customers for use on the face and the body, please contact our Sales Team.

Contact Our Sales Team