cosmetic viscosity
Article by: Perry Romanowski

When creating cosmetic products in a lab it is easy to have control over the final characteristics of your formula. Under this setting you get the maximum control over everything such as mixing conditions, raw material consistency, and ingredient amounts. Your finished formula will have the most reliable characteristics in terms of physical and chemical properties.  However, in production you won’t have such controls. This is why you need to include ingredients in your formula specifically to adjust production variation.  Let’s examine some of these ingredients. cosmetic adjustment ingredients

Product Specifications

The first thing to understand is that every formula will have a range of specifications it needs to achieve for quality control purposes. As the formulator and product creator it is your responsibility to set the specifications for the formula.  The exact characteristics and ranges you include in your specifications will depend on the type of formula you are making, its expected aesthetic and performance characteristics.  The most common specification parameters for most cosmetics formulas are pH and viscosity.

pH adjusters

Most personal care and beauty products contain water. When this is the case pH is a convenient parameter for which to set a specification. The pH of a system tells you a lot of information such as

  • Chemical changes – if there is a chemical reaction going on in your system it may result in a pH change.
  • Performance – some products perform optimally at specific pH ranges. For example, hair conditioners work better when formulated at a pH around 4.0
  • Safety – Products that are too high or too low in pH may result in burns or skin irritation. Also, some preservatives will not work outside a certain pH range.

Typically, you set a pH range of a half a unit. For example, the pH range for a shampoo might be pH 5.0 – 5.5.

Sometimes what happens in production is that the pH of the final batch will be outside the specification range. Since production won’t want to discard the product they’ll come to you for suggestions on how to “save the batch.”  This is where adjustment ingredient come in.  When you are formulating a water containing cosmetic be sure to include an acid and a base in the formula.  The acid will allow for adjusting the pH down and the base will allow for upward adjustment.  These ingredients won’t have much impact on the product but they will make it easier in production.

 When you are formulating a water containing cosmetic be sure to include an acid and a base in the formula.

Viscosity adjusters

Another important property for cosmetic products is viscosity. This is one for which you’ll frequently have problems in production.  Viscosity is a measure of the rheology and thickness of the formula. When you are creating your formulations you’ll need to set a viscosity specification. The range will depend on your target viscosity but a 10 – 20%  value is not unreasonable.

The exact ingredients to include in your formula for viscosity adjustment will vary with formulations and depends on how you achieved a certain thickness in the first place. For surfactant systems salt can often be used to adjust the viscosity. Also acids and bases can have an impact on the viscosity. A salt curve analysis can be most helpful.

For other systems it is recommended you do a cosmetic knock out experiment on your formulation to see the effect that each ingredient has on the final viscosity.  This will give you an idea of what ingredients you can increase (or decrease) to adjust viscosity.

Since viscosity also is related to the manufacturing procedure you may not be able to adjust it by simply increasing some ingredient. For emulsion systems your first attempts should usually involve reheating the batch, mixing and cooling.

Color adjusters

The final color of a product is another thing for which you should set a specification. Even if you do not have an added color some of the raw materials may be yellow and can impact the final color. For this reason you might include an ingredient like Violet #2. A small amount of it can be added to off-set a yellowish tint. For colored products the dyes should be good enough for making color adjustments.  But sometimes if the color is too far off you might have to make another “color free” batch and blend the two together. Color blending of lab batches can help guide you on how much to blend to get the right final color.

Odor adjusters

Our last common parameter of formulas is the product odor. If you are including a fragrance in the product then that will be a suitable adjustment ingredient. However, in some formulation there is no fragrance. For these products you may have to include an ingredient that can off-set any malodors that might come in from your raw materials. There are a few types of odor absorbing raw materials that can be included such as cyclodetrins, triakyl citrates, and zeolites.

When making cosmetic products each ingredient should be included in your formula for a specific reason. Sometimes those reasons are for product functionality, other times they are for improving product aesthetics. But you also need to include adjustment ingredients just to ensure your manufacturing people are able to produce the formula within specifications every time.

About the Author

Perry Romanowski

Perry has been formulating cosmetic products and inventing solutions to solve consumer problems since the early 1990’s. Additionally, he has written and edited numerous articles and books, taught continuing education classes for industry scientists, and developed successful websites. His latest book is Beginning Cosmetic Chemistry 3rd Edition published by Allured.

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