Potential hydrogen, or pH, refers to the acid-alkaline ratio of a substance, including the food you eat, the skincare products you use, or your skin itself. The pH scale ranges from 1 (most acidic) to 14 (most alkaline), with 7 is neutral. Our skin’s normal pH range is between 4.0 to 6.5, with 5.5 being the most optimum. Our skin is naturally a bit acidic as it serves as the body’s first defense mechanism against foreign elements. Acidity serves to keep allergens, bacteria, wind, and pollutants out while keeping moisture in. However, when our skin is at a high pH, our skin will not be happy in an alkaline environment as its barrier function is impaired, so it becomes dehydrated and lets irritants dive in to create inflammation. And also enzymes that break down collagen are activated at higher pH levels, so you age faster. To help keep skin’s pH from getting out of whack, you need to pay attention to the pH level of your skincare products.
PH measurement is one of the most basic steps in creating skincare, not only does the pH of a product need to be compatible with the formulation and its purpose, but it also needs to work with the skin’s physiology and the preservation system of the formula. It is not only mandatory that the pH of the cosmetic products remain in a certain range to guarantee consumers’ safety, but it is also essential in product stability, and most importantly, in natural cosmetics, it is necessary for the performance of the preservative system you are using. Almost all of the preservatives we use in natural hair and skincare are weak organic acids or a salt of an acid, the solubility and the performance is extremely pH-dependent. It means, if you don’t keep the pH in a certain range, either your preservative will become insoluble and ineffective which affects the physical stability of the product, or it becomes less effective or completely non-effective depending on the pH. Making natural hair and skincare, as much as we like to avoid using synthetic colorants and rely on plants oils and herbal extracts to show their beautiful colour, the colour is extremely dependent on pH. You need to keep the pH in a narrow range to avoid changing the colour of the product
In summary, the pH value needs to be
– compatible with formulation type
– compatible with skin
– compatible with the preservation system
The pH is essential for
– long-term product stability
– long-term preservative efficacy
The pH of Skincare Product
It is best to formulated products with a pH that falls in the range of normal, healthy skin. This range is most often cited as being between pH 4 and pH 7. Certain products have pH numbers outside this range such as from using an AHA or BHA exfoliant with a pH of 3.6. Acidic products cause mild disruption in the skin’s pH, and this stimulates the skin to produce key substances that make the skin to look smooth, supple, and hydrated.
On the other hand, using highly acidic (pH 2.5 or lower) or alkaline (pH 8 or higher) products cause a more significant disruption in skin’s pH, so it takes skin longer to get back to normal. During this extra time, the skin is vulnerable to factors that can trigger breakouts, signs of eczema, redness, and sensitivity. That is why daily use of products with too high or low pH is causing visibly and progressively damages to the skin
As a reference, during your formulation, it is great to achieve the pH ranges for each of these skincare product categories : –
Ideally, making skincare that has a pH of around 4.5 to 5.5 works well with the skin’s pH.
Measuring the pH is measuring the concentration of the hydrogen ions in a solution. The higher the concentration of these hydrogen ions, the lower the pH is and consequently, the lower the concentration of the hydrogen ions, the higher the pH is. Where there is no water, there are no hydrogen ions. You will need to check the pH of any product that contains water, such as toners, emulsions, shampoos, body washes and more. You cannot measure the pH of a non-aqueous product such as an oil blend or a balm. Even if you disperse your balm or oil in water, it is the pH of the water you are measuring and not the pH of the product.
PH Measuring Tools
For pH measurements, you can use pH strips or pH meters.
Paper pH strips
You can find two kinds of paper strips on the market:
– one with graduation 1
– one with graduation 0.5.
It is needless to say 0.5 graduation is better as it can give you a more accurate pH reading. You can get graduation at 0.5 graduation here.
pH meters are one of the best tools for pH measurements as they do give a more accurate reading than pH strips. There are so many good and affordable pH meters on the market, from portable ones to bench top meters. These devices need to be looked after, they need to be calibrated at regular intervals, but the supplier should provide you with instructions. For a start, you can get either Hanna Checker Plus or like this pH meter. However, as you progress, or you are going to make a lot of water containing products then go for this one that has a long wire connecting the pH meter body to the pH probe.
Measuring the pH
When you measure the pH of your cosmetic products such as creams, lotions, and shampoos, you need to dilute the product in distilled water, blend the mixture well and then measure the pH.
Step 1. Take a sample
Take a small sample of your product and transfer it into a clean, disinfected beaker.
It is a good idea to prepare more product to have some extra for pH measurement. This means if you are planning to have a 50g jar of cream, make 60g as your total batch so you can have the extra for pH control.
In the usual case, the sample you use for pH measurement is around 1g-5g only so not to waste your product.
Step 2: Make a dilution
PH is temperature dependent, wait until your sample reaches the room temperature and use room temperature water for your dilutions.
Dilute your sample in distilled water, with a ratio of 1:9, e.g. product to water ratio is 10% and 90%, respectively.
For example, if you have a 1g sample (10%), you will need to add 9g distilled water to it. Stir the dilution well.
Step 3: Check the pH
Although most modern pH-meters are equipped with a temperature sensor, if there are extreme temperature fluctuations in your country (icy cold in winter and hot in summer), you may even need to thermostat your samples for a few minutes before measurement.
- If you are using paper strips, dip it in the dilution and check the results using the chart on the packaging.
- If you are using a pH meter, dip it into the solution and keep it there till the reading stabilises. (Please also check the manufacturer’s recommendations.)
Adjusting the pH
When you measure the pH of the product, one of these 3 possibilities will be presented: –
Scenario 1: The pH of the product is exactly in the range that you want and in the range that your preservative system has the highest efficiency.
Scenario 2: The pH of the product is higher than your desired range, and you need to reduce it.
Scenario 3: The pH of the product is lower than your desired range, and you need to increase it
For scenario 1, it is the perfect case, but it rarely happened, and this means you need not do a single thing.
For the 2 other scenarios, you will need pH modifiers, ingredients that are added to adjust the pH of the cosmetic product. They are usually used in a very small percentage and added in the final steps of the formulation process.
When the pH of the product is higher than your desired range, you will need to decrease the pH: –
- Citric acid
Citric acid is usually sold as a powder (anhydrous or hydrated) or as a solution. Blend 10% citric powder into 90% distilled water. This means that you add 1g of citric acid powder to 9g distilled water.
- Lactic acid (solution)
Although originally a powder, is commercially available as an 80% solution (this is the max. available concentration commercially available). It is much more expensive than citric acid, and in 80% concentration, it could be quite corrosive (handle with care, avoid contact with skin). Lactic acid can generally be purchased at an 80% strength, and you can then dilute it further with distilled water to make 40%, 25% or 10% solutions.
Lactic acid is often used for its additional moisturizing benefits.
**Do not use vinegar, lemon juice or household cleaners to reduce the pH.
When the pH of the product is lower than your desired range, you will need to increase the pH: –
- Sodium bicarbonate (Baking soda) – readily available and use
Blend 10% Sodium bicarbonate into 90% distilled water. This means that you add 1g of pH modifier to 9g distilled water. Gentle heating may help with dispersion.
- Sodium hydroxide (NaOH)
Blend 10% Sodium hydroxide into 90% distilled water. This means that you add 1g of sodium hydroxide to 9g distilled water. ALWAYS add sodium hydroxide to the water not the other way around, or it will create strong fumes.
Powder to be added to the water phase. L-Arginine is an essential or semi-essential amino acid necessary for protein synthesis. When you dilute it in water (10%), it has a pH between 10.5-12, and this is a suitable base to increase the pH of your cosmetic products as it is quite easy (and safe) to work with. Compared to NaOH and baking soda, using L-Arginine is the mildest way to increase the pH of your products.
Both NaOH and baking soda are aggressive to the skin and very susceptible to moisture and oxygen. They absorb carbon dioxide, and their pH reduces upon storage. Nevertheless, since you are going to use just tiny amounts of these ingredients to lower the pH, there would be no residues of it in your finished product. You need not be concerned about the safety or harshness of your product. It is easily available and easy to use. So if this is the only available pH modifiers you have, go ahead and apply it.
How to use pH modifiers:
You only need to use a few drops of the pH modifiers to decrease or increase the pH of your product.
Once adjusted, repeat Steps 1-3 in the previous page to recheck the pH.
**PH modifiers are usually used in a very small percentage and added in the final steps of the formulation process. If you make dilution, keep them in tight bottles in a cool, dark place so that you can use them up in max 1 week.
Most ingredients are more susceptible to a high pH than to a low pH. Always try to add your pH modifier in a small amount so that you do not jump to a high pH. Some ingredients will immediately react to a high pH, and in such case, you will probably need to discard your batch and redo. If none of your ingredients reacts to high pH, all you need to do is reduced the pH to your desired point. Go back to the reducing pH by adding the acid as per the steps mentioned in the previous section.
Some products may not need dilution, such as toners or micellar waters. But it is good to make it your habit always to make a 10% dilution when you want to measure the pH of a product, to be on the safe side.