Milestones of Chemistry:


Ever since it was discovered more than 70 years ago, the silica AEROSIL® has proved to be an all-rounder—and its success story is by no means over. It all began when the inventor’s discovery was rejected.

“It’s much too expensive!” Harry Kloepfer’s bosses told him when he presented his latest invention to them in 1941. The innovative substance was a pyrogenic (pyrogenic = produced in a flame) or “fumed” silica that could replace carbon black as a filler in tire rubber. Kloepfer had invested four years of his life in this discovery—but now this time seemed wasted.

Fortunately, his supervisors at Degussa reconsidered their decision. As a result, the company began to produce silica under the brand name AEROSIL® in 1944. Kloepfer’s original idea of using AEROSIL® as a filler in tires was quickly rejected because it was indeed too expensive. However, the manufacturers soon noticed that silica is a real allrounder.

For example, when AEROSIL® is used as a thickening agent, it ensures that the viscosity of coatings remains flexible. Paint is viscous when it’s inside a can. However, stirring makes paint fluid so that it can be applied to surfaces without dripping. Once paint has been spread onto a wall, it quickly becomes firm again. As a result, AEROSIL® prevents the paint from running.

Fumed silica is also an outstanding flow improver. It coats the particles of active substances and thus makes them flow past one another more easily. This prevents spices from sticking together, for example. As a flow improver, AEROSIL® also makes it possible to precisely dose materials in the right amounts.

Flowability of powder
Flowability of powder

Moreover, silica is used as a thickening agent for rubber and silicone in pacifiers and shoe soles, for example, and it’s also employed as an abrasive. No matter what it’s used for, the fluffy white powder is inconspicuous but very effective. Instead of taking center stage, this substance helps other materials bring their strengths fully to bear.

This genuine jack-of-all-trades is manufactured at eight production facilities worldwide, from Antwerp in Belgium to Waterford in the USA and Yokkaichi in Japan. In keeping with Harry Kloepfer’s inventive spirit, these facilities are still researching this miraculous white substance and coming up with new innovations.



AEROSIL® is produced from compounds such as silicon chloride (SiCl4) by means of flame hydrolysis. The chloride is first vaporized, then mixed with air and hydrogen and forwarded to a combustion chamber. The powdery white silica is created under the flame within a few seconds. The silica is left to cool, and then the solid matter is separated from the associated gases.

Hydrophilic and hydrophobic AEROSIL®

Hydrophilic AEROSIL® is untreated silica and is divided into mixed oxides and silicon dioxide. Hydrophobic AEROSIL®, on the other hand, is created by chemically treating hydrophilic silica with silanes, silazanes or siloxanes. It’s called hydrophobic because this silica absorbs very little moisture. As a result, coatings containing hydrophobic AEROSIL® are extremely well protected against moisture and rust.

Short biography


Harry Kloepfer was born in Berlin in 1887. He studied chemistry at Berlin Technical University, where he earned a doctoral degree in 1922. In 1925 he was hired by Degussa, where he was appointed the Head of Inorganic Research in 1940. At Degussa, Kloepfer investigated a wide variety of organic chemistry topics, focusing in particular on the development of fumed silica. Then in 1944 the company began producing AEROSIL®, which is still one of its most successful products today. In 1950 Kloepfer was granted power of attorney over the main Degussa facility in Frankfurt. Although he retired in 1962, Kloepfer continued to serve Degussa as a consultant for several years. He died in Bad Homburg in 1973.


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