From daily lotions that keep skin soft to moisturizers for refreshing face wash, lotions are synonymous with protecting and nourishing the skin. These cosmetics are essential to many people, and the science behind them is very fascinating. 

When you successfully mix two or more fluids that normally don't mix well, an emulsion is formed. Imagine mixing oil and water and actually let them gel together to form a new substance. This new substance is an emulsion, and the process of mixing fluids together is called emulsification.

Lotions, creams, and moisturizers are cosmetic emulsions—water-based mixtures of light, non-sticky oils, fats, waxes, and other raw materials. Since these lotions are water-based, they help the skin maintain its moisture content and prevent moisture loss.

In the emulsification process of cosmetic lotions, creams and moisturizers, very small droplets of fat, oil or wax are suspended in a fluid (usually water) and dispersed evenly. Then divide these incompatible liquids into several layers. The lower density substance, such as oil or wax, is in the upper layer, while the densest water is in the lower layer. When the correct surfactant is added to the mixture and stirred vigorously, the oil or wax will disperse in the water to form an emulsion. 

The type of equipment used to emulsify incompatible liquids is the most important factor in this process. Whether it is simple or complex, the emulsification equipment decomposes the substances in the inner phase and disperses them in the outer phase to form small particles to ensure no oil seepage or stratification during stability.

Currently, there are three types of emulsifiers: agitators, colloid mills, and homogenizers. The results vary with the size, structure, and performance of these devices, which usually affect the dispersion and stability of the final product. In other words, the size of the particles in the emulsion and the quality of the emulsion itself depend to a large extent on how these equipment handle and stabilize the components.

Among the three, the performance of the agitator is the worst compared with the colloid mill and the homogenizer, and both are better in emulsifying incompatible substances. In recent years, with the advancement of emulsification technology, vacuum emulsification mixers have emerged. These equipments can prepare emulsions with excellent dispersibility and stability, thereby producing more delicate and smooth emulsions and creams. In addition to equipment, temperature and time also play an important role in the emulsification process. These two factors mainly affect the quality of the final product.

Generally speaking, the temperature part of the process is usually carried out in two stages. The first stage involves the highest melting point of each substance, and the second stage involves solubility. At each stage, the temperature must be monitored very closely. For example, if the viscosity increases significantly during the emulsification process, the temperature can be appropriately increased.

As for determining the time involved in the emulsification process, it depends on the volume ratio of the oil phase to the water phase, the viscosity reached during the two temperature phases, and the resulting emulsion. 

Since cosmetic emulsions are applied directly on the skin, the quality of these products must be strictly tested and analyzed. The centrifugal separation experiment achieves this by testing the stability and shelf life of cosmetic emulsions (such as facial cleansers, body lotions, and hair dyes).

These experiments were carried out with a low-speed centrifuge and thermostat. The number of revolutions and time vary from product to product, but in general, when the sample is placed in the centrifuge, the sample will rotate at a speed of 2,000 to 4,000 revolutions per minute at 30-minute intervals. This allows for observable separation and delamination of the product.

For example, in a basic facial cleanser product, the sample needs to be centrifuged at 2,000 revolutions per minute for 30 minutes. For skin care lotions, the quality is determined based on separation. High-quality emulsions will not emulsify after centrifugation at 4,000 revolutions per minute in 30-minute intervals. The lower the number of revolutions, the lower the quality of the final product. 

Ohaus FC5706 centrifuge. Image source: OHAUS OHAUS FC5706 Centrifuge is a highly efficient device that can achieve results in the development of emulsion cosmetics.

The OHAUS FC5706 centrifuge is designed to be lightweight and compact, with ergonomic knobs, intuitive panel design and dual safety controls that can monitor the system and its speed. During the centrifugation process, our equipment works quietly in the background to maintain a quiet and comfortable laboratory environment.

The device has three rotors and seven centrifuge tubes with capacities ranging from 1.5 to 50 ml. The time range can be set up to 99 hours and 99 minutes. 

Ohaus FC5706 centrifuge is a medium and low speed equipment specially designed for the cosmetics industry. 

Learn more about Ohaus centrifuges

https://www.karenrosalie.com/blog-all/2017/8/11/the-difference-between-emulsion-and-serum https://www.sciencedirect.com/topics/chemical-engineering/emulsification

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