Lab reactors for cosmetic industry

Kai-Oliver Linde details the technical solution to better cosmetic products 

In the process of developing cosmetic products at laboratory scale, it is very common for many laboratories to perform the majority of production steps separately and manually.

But it is much more convenient and easier to produce cosmetics or reproduce cosmetic production processes on a smaller scale.

Working with a complete reactor-system, which allows controlling of all necessary processes taking place, while developing new products or finding solutions to problems in the production area, is a far more efficient approach.

IKA offers a complete solution to the cosmetic industry, from small-scale 500mL to 4,000L reactor systems.

With its laboratory reactor systems such as the LR.2-ST and the LR 1,000, the company combines the most important processes needed in the production of cosmetics in one device.

The reactor is designed for products such as lipstick, lotions, shampoos, ointments, creams of all sorts, colloids (gels), eyeliner, mascara, etc.

A number of processes are of interest during the development of a cosmetic product. This includes, amongst others, mainly the stirring, homogenization, heating and cooling (temperature measurement and control), pH measurement, vacuum, torque-measurement (viscosity) and data collection through software.


In many applications for cosmetic products the first step is to bring an oil- and water-phase (o/w; w/o) together and homogenize it to a degree that a stable emulsion is created, supported by a proper chosen emulsifying agent.

Typically, homogenizers such as the Ultra Turrax T 25 digital are used for such challenges. By choosing the right rotor stator geometry of a dispersing tool, different degrees of fineness can be obtained, down to 1μm.

The fast-turning rotor of a dispersing tool creates a suction effect and forces the oil through the teeth of the stator.

In the gap between the rotor and stator the actual homogenization process takes place. The shear-rate depends on the circumferential speed and the size of the gap.

The higher the shear rate, the higher the energy introduced into the emulsion. The oil droplets get finer and finer and finally reach a size where they can form a stable emulsion.

The emulsifier will stabilise the emulsion to keep it from separating again.

The smaller the oil droplets are, the more stable the emulsion will appear. One of the best-known examples for an emulsion is milk with lecithin as emulsifier.


While the oil and water phase are homogenized the product is usually stirred at the same time to speed up the process and allow it to be most thoroughly mixed inside the reaction vessel.

When the viscosity of the product rises it is of especially high importance to use scrapers on the stirring element inside the stirred vessels wall and bottom to keep the product in motion and move it back into the centre of the vessel and away from the walls.

If other ingredients are added to a more viscous product these should be distributed evenly throughout the whole product. This is of particularly high importance when producing pharmaceutical products such as ointments, which contain an active ingredient.

Heating and cooling

Heating and cooling allows the user to first heat up the oil phase, which could also be a wax that is solid at room temperature. Instead of heating the oil phase separately on a heating plate or magnetic stirrer, it can be performed right within the reactor-system.

At the end of the product’s formulation it is usually cooled down to room temperature.

By using double-walled glass reactor vessels it is easy and convenient to heat and cool the product with an oil- or water-thermostat, depending on what temperatures are required. If a thermostat is connected to a temperature sensor that is placed into the product inside the reactor, the temperature of the oil surrounding the product can be controlled in a way that the products temperature will be most exact.

Torque measurement 

Cosmetic products show a change in viscosity during the production process. These allow further interpretation of the products’ comparison to other batches, behaviour, stability and sensitivity to certain influencing variables that can be changed.

Viscosity measurements require removing sample material from the vessel during the process and do not allow a continuous interpretation.

The Eurostar control stirrers allow monitoring of these changes during the actual process of producing the cosmetic or pharmaceutical product. By interpreting the required motor power of the stirrer (motor) as a viscosity change, it can be made visible how the product reacts on for example the heating or cooling rate.


When looking at highly viscous products such as ointments, or especially colloids (gels), vacuum is a ‘must-have’. It turns out to be a very difficult and time-intensive task to remove air bubbles from the product.

Using vacuum and sometimes slow stirring during the production and/or after, allows minimising, or sometimes even avoiding, the effect of air in the product.

Besides all the above-mentioned properties of a laboratory reactor, further requirements are needed for different types of applications.

These include, for example, pH measurement and flexibility of a reactor to attach other accessories (reflux coolers, dosing devices etc.).

There is a huge amount of possible requirements, and that is why IKA’s reactors are equipped with standard fittings NS 29 and NS 18 – so they can be fitted to almost any application.

All measurement data can be collected with the Labworldsoft software, which allows controlling of the reactor system along with storing, displaying and exporting to programs such as Microsoft Excel, for example.

Flexibility is one of the required properties nowadays. Users expect their machines to be able to adapt to the fast-changing requirements of product developments. These reactor systems are designed provide that flexibility.

Kai-Oliver Linde is with IKA Werke.

Recent Issues