Cosmetics knowledge: Adjusting the pH value

The pH value is not only important for the skin. Some active ingredients and especially preservatives sometimes require a specific pH value in the end product so that they do not lose their effectiveness.

 

The following applies in principle to measuring:

• Only water-based formulations can be measured.

• Once you have finished stirring and all ingredients are in your product, you should check the pH value again. You can use our pH test strips or a pH meter for this purpose. The latter, of course, provides you with very accurate values in the 0.1 range. If you use such a device, ensure that the probe is always well rinsed and that no product is adhering to it when measuring, as this could falsify the (subsequent) measurement result.

 

If your pH value is not where it should be, you have two options:

• Lower the pH value (with acid),
• or increase the pH value (with an alkali).

Usually, you will need to lower it slightly.

 

The following applies in principle to adjusting the pH value:

• The pH value is adjusted using a diluted solution and not, for example, with pure citric acid, lactic acid, sodium hydroxide, or arginine. You should therefore prepare a solution beforehand that you can then use for this purpose. Using a concentrated pure product (e.g., crystalline citric acid) could be too strong for your end product. For example, the strong acid could cause an emulsion to separate when added!
• The pH value is adjusted step-by-step by adding a few drops of the solution, then checking again, then stirring in a few more drops, checking again, etc. Tip: use a pipette for this.
• Whenever you add a few drops of the solution, you must stir thoroughly before checking the pH value again.

How do you prepare a solution for pH adjustment?

The most frequently used agents are a citric acid solution for lowering and caustic soda (sodium hydroxide solution) for increasing the pH value. If you use both in the same product, a portion of the citric acid is converted into sodium citrate by the alkali. Together with the active citric acid, this leads to a stabilization of the pH value. This is referred to as a "buffer." As a rule, this is important to ensure that the pH value of the finished product does not change even after a long period of time.

 

• For a citric acid solution, one usually uses 50% citric acid and 50% distilled water. You only need to weigh out the ingredients (e.g., 20 g of citric acid and 20 g of water) and stir them together. Remember to always weigh all ingredients - milliliters are only equivalent to grams in the case of water and are therefore generally not a suitable unit of measurement for cosmetics production! Then stir the two components thoroughly together. This can take a while until the citric acid crystals have completely dissolved. It goes faster if you warm the solution slightly. Due to its extreme pH value, the citric acid solution is shelf-stable for a while even without preservatives. You can fill it into small bottles, store it, and use it again and again to adjust your products.
• Those who wish to enrich their product with moisture at the same time can also use our Regenine to acidify the pH value. You can even use this undiluted, as it is already a diluted acid solution.

• For a diluted caustic soda solution, a 10% solution is typically used. For example, 5 g of sodium hydroxide (NaOH) and 45 g of water. Remember that this solution is somewhat caustic, so wear safety goggles! In the product itself, the alkali is neutralized, and you do not need to worry about it harming the skin. Like the citric acid solution, you can store the caustic soda solution well-sealed in a clean glass and reuse it.
• Sodium bicarbonate (= baking soda) or sodium carbonate can also be used to increase the pH value, but this is done less frequently because you need more of it, making it easier to "water down" the product. However, you can just as easily prepare your alkaline solutions from it. Sodium bicarbonate, however, does not dissolve as quickly. We would advise against storing a sodium bicarbonate solution, as the pH value is not as high, depending on the concentration.

 

In which products is the pH value not adjusted?

As already mentioned, everything here refers to water-based products, as a pH value is only relevant there. Water-containing products must almost always also be preserved, which is why checking the pH value is particularly important here. Remember: Preservatives based on organic acids (such as levulinic acid, benzoic acid, sorbic acid, anisic acid, etc.) require an acidic pH value to work at all. The more acidic, the higher the effectiveness! This is the case, for example, with our Preblend Aqua.

 

Products that do not require adjustment are:

• purely fat-based products (sticks, balms, fat ointments, etc.)
• purely alcoholic products (perfume)
• special products: Certain products that have a high or low pH value and require it. Soaps, for example, are always alkaline. This cannot be changed because they would not be stable otherwise. Also, with baking soda-based deodorants, it must be considered that they work precisely because the pH value is so high (the bacteria on the skin cannot multiply). If one were to adjust the pH value here, the acid would neutralize the baking soda and the effect would no longer be present. Other examples of special products would be: depilatory creams, hair dyes, perming agents, alkaline skin care products, fruit acid products, etc.

 

What pH value does my product need:

As a rule of thumb, you can remember the value 5.2 (5 - 5.5) for most skin products such as emulsions and surfactant products (shower gel, shampoo)! This is in the slightly acidic range, is mild to the skin, acid-based preservatives (Preblend Aqua) work quite well here, and surfactant products (shower gel, shampoo) exhibit the best consistency at this level.

For hair care products (conditioners), it can be a bit more acidic: 4 - 4.5. The acidic effect here ensures that the cuticle of the hair closes.

A slightly acidic pH value is also an advantage for toners (facial toners): 4.5 - 5. After washing, the toner ensures that the acid mantle can regenerate more quickly.