Dr. Frank Preston, prolific inventor
The founder of American Glass Research, Dr. Frank Preston, is well-known for his seminal work in fractography and glass container testing. His roles as an amateur naturalist and conservationist are also widely recognized in western Pennsylvania. But did you know that Dr. Preston was also a prolific inventor?
In the summer of 2019, AGR began digitalizing our archives of early papers that stretch back into the 1920s. Among the yellowed stacks were at least 60 patent ideas recorded by Dr. Preston in various levels of detail, often witnessed by a notary to establish the date of invention. (Until 2013, the USA used a first-to-invent patent system, so proving the date was critical.) Some of these ideas are so prescient that glass technology would not catch up with them until decades later.
For example, a memo to a chemist in 1931 proposes a “solar glass” that would darken when exposed to ultraviolet light. Dr. Preston notes that this reaction must be “rapid and reversible,” and could perhaps be accomplished by a silver salt. In the letter’s closing, he encourages the recipient that “you will no doubt find the working out of the details very simple.”
As history would have it, photochromic glass was invented in the 1960s by a chemist at Corning Glass Works. This type of glass changes from transparent to a darker grey when exposed to UV light, and does in fact rely on silver chloride, a type of silver salt. The color fades after a few minutes in the absence of UV. Almost everyone has seen this type of glass at work in so-called “transition lenses” used for glasses. Although most modern photochromic lenses are made from plastic due to their lower weight, the glass version is still available.
By 1932, Dr. Preston had abandoned the idea of a photo-sensitive glass in favor of heat-reflecting glass that “let sunlight into a building in adequate amounts while excluding the heat rays as much as possible.” He posited that “if a suitable metal can be incorporated in the glass in the metallic form…or deposited on the surface…a high reflecting power in the infrared together with considerable transmission in the visible can be attained.”
This idea came to fruition in the 1970s, largely as envisioned by Dr. Preston, in the form of “low emissivity” glass or simply “low-e” glass. Many varieties of low-e coatings currently exist, but virtually all are in the form of thin layers of silver and/or other metal oxides deposited on the surface of architectural flat glass. Windows or glazing equipped with low-e glass are commonly used in commercial and residential buildings for the enormous savings they provide in heating and cooling costs. One wonders what would have happened to AGR as a company if Dr. Preston had pursued this idea!
Although this article has focused on Preston’s insights into future glass inventions, there were many other less practical patent ideas that never saw the light of day. What would the world have been like if it had leg-attachable air bladders for men who have trouble floating? We can only wonder.