Ultrasonic Milling for Lipstick Manufacturing

Lipstick manufacturing involves the grinding and mixing of waxes and colour pigments on a precisely controllable level to ensure a certain colour and texture profile of the lipstick. Ultrasonic grinding and mixing is a reliable, efficient, and exactly controllable technique to produce highly homogeneous wax/pigment slurries for the production of high-quality lipsticks.

Ultrasonic Mixing and Grinding for Lipstick Manufacturing

In general, the manufacturing of lipsticks is done in small to medium size batches, since the composition of each lipsticks variation varies in colour / shade, glossiness, ingredients (nourishing compounds) etc.
Lipstick manufacturing involves various raw ingredients such as waxes (beeswax, candelilla wax, camauba), pigments (e.g. organic and inorganic, pigments, carmine; plant-derived pigments, mineral pigments such as micas, oxides, ultramarines), alcohol (solvent), oils (mineral, castor, lanolin, or vegetable oils) and additives (preservatives, antioxidants, caring ingredients, fragrance). In general, the ratio of oil:wax:pigment is approx. 50-70% : 20-30% : 5-15%, respectively.
Those ingredients are melted and stirred in separate batches: one batch contains the solvents, the second batch contains the lipids / oils, and the third batch contains the fats and waxy materials.
To incorporate the colour pigments, the solvent solution and heated liquid oils (approx. 180°F or 85°C) are mixed with the color pigments by stirring in order to form a crude premix. The premix is fed into an ultrasonic flow-through reactor, where the pigment slurry is treated with intense ultrasonic (acoustic) cavitation. Ultrasonic cavitation is a purely mechanical treatment, which is based on extreme shear forces and inter-particular collision. Ultrasonic milling and grinding allows for a precise process control and thereby a continuously high quality output.

The ultrasonic milling and grinding reduces the particle size of the pigments uniformly so that a smooth texture is obtained. This is an important step since the texture of a lipstick is an essential quality mark and a grainy feel is undesired. Furthermore, the uniform particle size distribution is crucial to obtain tinting strength and in-depth colouring of the lipstick.
Whilst conventional high-shear mixers, roller mills and bead mills introduce air into the oil/pigment slurry, inline sonication avoids the entrapment of gas bubbles. Ultrasonication has even de-aerating / degassing effects, which makes the subsequent step of de-aeration by vacuum superficial. By avoiding the deaeration step, processing costs and time are reduced.
In a mixing second step, the pigment/oil slurry is combined with the hot wax. The mixing of pigment/oil and the hot wax can be done by the ultrasonic mixer, too. 
Finally, the lipstick mixture is poured into molding tubes, where the lipstick is cooling and hardening whilst obtaining its typical stick form. As soon as the wax/pigment mixture has got solid, it can be inserted into a plastic or metallic packaging and is ready for sale.

High-Performance Ultrasonic Mixers for Lipstick Manufacturing

Hielscher Ultrasonics supplies high-performance ultrasonicators to cosmetic manufacturers worldwide. Ultrasonic milling, grinding and dispersing is a reliable and efficacious technology to produce homogeneous mixtures consisting of waxes, lipids, O/W or W/O emulsions, pigments and nourishing additives. Ultrasonic mixers easily handle highly viscous slurries such as wax melts, high particles loads, and pastes. Even the handling of very abrasive particles is no problem for ultrasonic mixing and milling systems.
Ultrasonic processes can be run in batch and in continuous inline operation. Especially for larger lots, ultrasonic inline processing using an ultrasonic flow-through reactor offers various advantages, including higher product uniformity, since the retention time in the sonication area and the processing temperature can be precisely controlled. Using an ultrasonic inline system with flow cell prevents the entrapment of air bubbles and provides even de-aerating / degassing effects.
Hielscher Ultrasonics is long-time experienced in the design, manufacturing and distribution of high-performance ultrasonicators for the production of cosmetic products. We assist our customers from first feasibility test and process optimisation to the installation and operation of the industrial-size ultrasonic dispersing unit.
Hielscher Ultrasonics’ industrial ultrasonic processors can deliver very high amplitudes. Amplitudes of up to 200µm can be easily continuously run in 24/7 operation. For even higher amplitudes, customized ultrasonic sonotrodes are available. The robustness of Hielscher’s ultrasonic equipment allows for 24/7 operation at heavy duty and in demanding environments.
The table below gives you an indication of the approximate processing capacity of our ultrasonicators: