# How the Float Glass Process Makes Perfectly Flat Window Panes > This 1954 patent describes the float glass process, a method for creating high-quality, perfectly flat glass by floating molten glass on a bath of liquid metal. - **Patent:** US 2911759 - **Original title:** Manufacture of flat glass - **Owner:** Pilkington Brothers Ltd - **Granted:** 1959 - **Status:** Public domain (expired) - **Times cited:** 53 - **Field:** mechanical, materials, automotive, consumer_electronics ## What it does The invention describes a continuous manufacturing process where molten glass is poured onto a bath of molten metal, typically tin. Because the glass is less dense than the tin, it floats and spreads out to form a perfectly flat surface. As the glass ribbon travels along the surface of the molten metal, it is cooled and solidified before being lifted off. This method produces glass with a uniform thickness and a fire-polished finish, eliminating the need for expensive mechanical grinding and polishing. ## What it does NOT cover - Does not cover the production of glass using traditional rolling or drawing methods. - Does not cover the chemical composition of the glass itself, only the forming process. - Does not cover the specific equipment used for cutting or tempering the glass after it has solidified. ## The clever bit The genius lies in using a molten metal bath as a perfectly flat, frictionless surface that shapes the glass through gravity and surface tension alone. ## Real-world examples 1. Modern skyscraper windows 2. Automotive windshields 3. Residential glass doors 4. Display glass substrates ## Why it matters Before this invention, flat glass was expensive and labor-intensive to produce because it required grinding and polishing both sides of the glass to achieve clarity. The float glass process revolutionized the construction and automotive industries by making high-quality, distortion-free glass affordable and mass-producible. ## Frequently asked questions ### What does How the Float Glass Process Makes Perfectly Flat Window Panes cover? This 1954 patent describes the float glass process, a method for creating high-quality, perfectly flat glass by floating molten glass on a bath of liquid metal. ### Who owns patent US 2911759? Pilkington Brothers Ltd owns this patent, granted in 1959. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 2911759 cited by? This patent has been cited by 53 later patents that build on its ideas. ### What problem does this patent solve? Before this invention, flat glass was expensive and labor-intensive to produce because it required grinding and polishing both sides of the glass to achieve clarity. The float glass process revolutionized the construction and automotive industries by making high-quality, distortion-free glass affordable and mass-producible. ### What does this patent NOT cover? Does not cover the production of glass using traditional rolling or drawing methods. **Full plain-English explainer:** https://patentbrief.org/patent/us/2911759/float-glass-pilkington **Original patent:** https://patents.google.com/patent/US2911759 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How Glass Fibers Are Spun for Insulation](https://patentbrief.org/patent/us/2133235/fiberglass-glass-wool-slayter) — A 1933 invention by Games Slayter that describes the process of melting glass and blasting it into fine, flexible fibers to create insulation. - [How Car Windows Use Special Coatings to Balance Privacy and Visibility](https://patentbrief.org/patent/us/6033785/vehicular-colored-glass-pane-with-light-transmittance-and-reflectance-adjustment) — A patent for automotive glass that uses a specific combination of tinted glass and multi-layered coatings to keep the inside private while ensuring the driver can see out clearly. - [How Corning Invented Modern Fiber Optic Cables](https://patentbrief.org/patent/us/3711262/optical-fiber-waveguide) — A 1970 method for creating glass fibers that carry light over long distances by layering glass inside a tube and drawing it into a thin, solid strand. - [How Chemically Strengthened Glass Works](https://patentbrief.org/patent/us/3778335/gorilla-glass-chemically-strengthened) — A 1971 Corning patent describing a specific chemical recipe for glass that can be made incredibly tough by swapping small atoms in its surface for larger ones. - [How the Modern Waterbed Works](https://patentbrief.org/patent/us/3585356/waterbed-liquid-support) — A 1971 patent describing a liquid-filled, heated furniture support designed to cradle human bodies without letting them touch the bottom of the container.