When making skin and hair care products, it is important to be mindful of pH. It’s easy to forget this important step, as we tend to focus on the more obvious product attributes, like smell and texture. While it is important for a product to look, smell and feel good it is also very important to ensure that the product exhibits the correct pH for its application. Doing so is a matter of safety and efficacy. You can spend time selecting just the right ingredients and making sure your product looks and feels and smells just right, but if the pH is incorrect, all of your efforts can be wasted.
What is pH?
The initials “pH” stand for “potential of hydrogen” as pH is the measure of hydrogen ion concentration in a given solution or substrate. The pH scale is logarithmic, so as a result, each whole pH value below 7 is ten times more acidic than the next higher value. For example, pH 4 is ten times more acidic than pH 5 and 100 times more acidic than pH 6. So it’s clear that moving from a pH of 5 to a pH of 4 or 3 can have serious consequences. Pure water has a pH of 7 and is considered neutral. As you move away from pH 7 in either direction the ramifications of each step on the pH scale become greater.
Also, pH can sometimes be directly related to the functionality of a product. For example, the preservative potassium sorbate functions properly at a pH of 4.5. If this guideline is not followed then the product’s efficacy and shelf life may be greatly compromised. The same applies to products like acid peel face masks, if the pH is too low, it may result in a trip to the emergency room with potential life changing effects.
Skin has a protective layer on its surface called the acid mantle. The acid mantle is made up of sebum excreted from the skin’s sebaceous glands. The sebum mixes with lactic and amino acids from sweat creating the skin’s pH, which ideally should be somewhere between 4.5 -5.5. All skincare products should be tested to ensure they remain within this range. A good practice is to test pH directly after making the product, and again in 30 days to make sure the pH hasn’t changed. pH can be affected by a variety of reasons including ingredients, especially preservatives. Selecting the correct preservative for both the application and efficacy are important and many preservatives have a pH range in which they are considered to be most effective. In fact, some preservatives will not work at all if pH is out of the suggested range.
The human scalp is obviously still skin, so the pH range is 4.5-5.5, however, the hair shaft pH is 3.67. Any product applied on hair that has pH higher than 3.67 causes an increase in the negativity of the electric network of the hair, that is, an increase of static electricity and the repulsion between strands. The fiber surface bears a net negative charge because of its low isoelectric point. Positively charged ions are attracted to the negatively charged surface, thus helping to overcome the electrical barrier for anions.
When we rinse our hair, the water leaves both the scalp and hair shaft at a pH of about 7. This can cause issues with the scalp and can cause hair to be frizzy and easily tangled. Therefore an increase in negativity occurs. The negative electrical net charge generated will tangle the hair and make it hard to comb, thus causing the frizz effect. In alkaline pH, hair has increased capacity to absorb water. Water penetrates the scales that open, hydrating the strand and breaking the hydrogen bonds of the keratin molecule.
Essentially, you will need to decide what effect you want your product to have on the hair to determine its ideal pH. If you desire more volume, a higher pH might be beneficial. If you desire smooth and static free, a lower pH would make sense. We have found that generally, a pH of 5 is a good balance for both hair and scalp.
pH and Color
pH can have a drastic effect on color, especially when using natural colorants such as Beet Juice Powder. This lovely powder can become light pink to deep dark purple to completely clear and neutral depending on the pH. It’s best to test your colorants in different pH solutions to determine if the pH of your product will allow you to have the color you desire.
How to Test pH
Testing pH is actually pretty easy! You can use pH strips to quickly and easily determine the pH of your product. Simply dip the colored end of the strip into your product, and compare against the color-coded chart on the box of your pH strips. If you are making products that are colored or too dark to read on your pH strips, consider using a pH meter. You can watch our pH instructional video on how to use both and be sure to subscribe to our YouTube Channel for more videos.
Follow along with Teeneke in this video:
Please feel free to post any tips and tricks about pH, we’d love to hear from you!
Sources: Gavazzoni Dias MR, de Almeida AM, Cecato P, Adriano AR, Pichler J. The shampoo pH can affect the hair: Myth or Reality? Int J Trichol. 2014;6:95–9. [PMC free article] [PubMed]