Emulsion Mixing with Cosmetics

Introduction

For many cosmetic formulators, the terms lotion and cream are interchangeable, as both involve mixing to create an emulsion. Many cosmetic emulsions are oil in water (o/w), where the oil phase is surrounded by the water phase, but there are many examples of water in oil (w/o) emulsions as well.

Typical cosmetic emulsion

A typical emulsion mixing process begins with heating the water phase and water soluble ingredients to 75‑80°C, depending on the procedure. This may include premixing a thickener such as xanthan gum with glycerin, which is then added to the water and other ingredients. In a separate vessel the oil phase is also heated 75‑80°C, which can include emulsifiers such as glyceryl stearate, and emollients in addition to the oil or butter used. Often these heating and mixing steps use a propeller impeller.

The emulsification mixing begins when both the heated water and oil phases are combined together, with further mixing to achieve homogenization. Once this is achieved, the product is allowed to cool with stirring.

To address the thickening product that develops as it cools, an anchor impeller is often used to scrape the product from the sides of the vessel back towards the center. After a certain temperature is reached during cooling the remainder of the ingredients will be added, such as preservative and fragrance. pH may be adjusted at this time as well.

Steps

As a sequence of steps, cosmetic emulsion can be listed as below.

Aqueous phase: Heat the water soluble ingredients -- with optionally included xanthan gum and/or glycerin -- to 80°C. Stir with an propeller impeller.
Oil phase: In a separate container, heat the oil phase -- with optionally included glyceryl stearate or emollients -- to 80°C. Stir with a propeller impeller.
Emulsion phase: Combine the aqueous and oil phases. At 80°C, use a propeller impeller to mix the two for at least 20 minutes.
Cool down: After 20 minutes of mixing, replace the propeller impeller with an anchor impeller. Continue to mix until the mixture cools down to 30°C.
Temperature-sensitive ingredients: Now that the mixture is cool, mix in any needed ingredients such as preservatives, fragrances, and coloring.
Adjust pH: Lastly, adjust the pH as needed to finalize the batch.

Caframo models for cosmetic emulsion

Caframo’s high torque line of overhead stirrers has been a popular choice for research and development labs in the cosmetics and personal care industries.

Popular models include:

The BDC6015 offers the widest range of speed settings, from 40 to 6,000 rpm.
The high torque capabilities of the BDC1850 enable mixing of creams as thick as 90,000 mPa·s.
The BDC3030 is a perfect balance of speed and power, mixing viscosities up to 50,000 mPa·s with speeds up to 3,000 rpm.
Both the BDC1850 and BDC3030 are compatible with the sweep impeller U044SW, frequently used during cool down phase, and designed to fit into a popular formulation size 4 L standard beaker.

Getting help

If you'd like free advice & support in choosing an overhead stirrer for your application, feel free to reach out to Growing Labs at hello@growinglabs.com or 1-833-476-9420. We've helped equip and supply hundreds of laboratories both cost- and time-effectively.

(Information courtesy of Caframo.)