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.
Original patent title: “Manufacture of flat glass”
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. Granted to Pilkington Brothers Ltd in 1959 with 53 forward citations, and it is now in the public domain.
Key facts
Coverage
What does this patent actually cover?
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.
The gap
What does this patent 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.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
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.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Modern skyscraper windows
Automotive windshields
Residential glass doors
Display glass substrates
Why it matters
The bigger picture
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.
Filed
December 6, 1954
Granted
November 10, 1959
Market context
Who's building on this
Companies in this space
The process is now the global standard for flat glass production. Major manufacturers like NSG Group (which acquired Pilkington), Saint-Gobain, and AGC Inc. continue to operate and refine these float glass lines worldwide.
Market impact
This patent effectively created the modern flat glass industry. It rendered older, inefficient manufacturing techniques obsolete and enabled the widespread use of large, clear glass panels in architecture and vehicles.
Claim 1 — Plain English
What this patent covers
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.
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.
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.
Patent Journey
From filing to expiry
PatentBrief Score
Impact Score
Early stage
Citation count
35/40
Highly cited
Claim breadth
0/20
Narrow claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$52K – $166K
Midpoint $104K · expired or expiring · industry ×2.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Concepts involved
Citations
Patent lineage
Cite this patent
Pilkington, L. A. B., & Kenneth, B. (1959). How the Float Glass Process Makes Perfectly Flat Window Panes (U.S. Patent No. 2,911,759). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/2911759/float-glass-pilkington
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
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.
Patent monitoring