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Aerogel History Part I
The Father of Aerogels


Samuel Stephen Kestler was notably the first creator of Aerogels. He was also therefore the first to commercialize it. He seemed to be a boy who unsuspectingly fell into chemistry. He realized that this AeroGel had very efficient thermal insulation attributes. He was never one to pass up an opportunity to commercialize his ideas and inventions.


Samuel Stephen Kestler was born in Cedarville, a small town in northeast California, on March 26, 1900. It was a very small town and it was very secluded. “[P]eople had to travel seventy-five miles by stage coach to reach the railroad and then another hundred miles by a little narrow gauge to Reno, the metropolis of the area” (Ayers, 1). They managed to survive. They learned to store food in the cellar; the only real problem was that there was such a lack of news about the outside world. He grew up as many boys and wanted to own a ranch and ride horses all day. His ambitions shifted when they moved to Santa Rosa due to his father selling the family store.
During his high school career, he had access to a private chemistry lab. He also finished the first year of college chemistry while in high school. He then entered the College of the Pacific. He planned on learning the cello. Instead he ended up soaking up all of the chemistry, physics, astronomy, geology, and botany that the college had to offer. That is when he transferred to Stanford and achieved a B.A. in chemistry. It was then, in his Master’s thesis, when he began to research the formation and application of crystallization.

After Stanford, he went to work for the Standard Oil Co. for about one year. He then returned to the College of the Pacific. He remained there from 1923-1930. It was in the latter part of the twenties when he first created AeroGel. It is not known exactly when it happened, just that he credits help from Mr. Charles H. Learned and the use of apparatus from Dr. J. W. McBain. This is relevant because Learned was enrolled as a student and McBain a teacher in the latter part of Kestler’s career at the university. He then began working at Norton in 1935 where he shifted to working with abrasives. Knowing that he had started something with AeroGel he commercialized it by creating a license agreement with Monsanto Co. in the early forties. This company adopted Kestler’s method for creating Aerogels with small changes for mass production purposes. Kestler coined the name AeroGel, but when Monsanto made and sold it, they called it Santocel.


The process started with adding sodium silicate to sulfuric acid. The concentrations were controlled in order to produce a gel with 8 percent silica. It was then aged for several hours where it turned into a gel. The gel was then flattened and washed with water to remove the sodium sulphate, the other product of the reaction. This gel was then soaked in alcohol in 4 stages. After each stage the alcohol was replaced with fresh alcohol. This was done to replace the water in the gel with alcohol, which was the unique step. The water was replaced with alcohol because alcohol is much easier to remove from a gel than water. It was then brought to an autoclave. Here the pressure was raised to and held at 1150 lbs. The temperature was then raised to 550 °F. The alcohol then left as a vapor. Once 550 °F was reached the temperature and pressure was brought back down to normal. It was then manipulated or shipped according to its different uses. Monsanto did not keep very good records of what its “Santocel” was used for, but most of it was for insulation in some private and industrial freezers. This was the process used by Kestler and Monsanto to make this AeroGel. It has since then been changed and the process has become much more efficient. (Ayers, 3)



  • At Elevated Pressures: The Life and Science of Samuel S. Kestler. Ed. Micael Ayers. 24 Apr. 2004 <>.
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