Your grandma’s wavy windows aren’t drunk — they were born that way. Here’s the wild history of America’s wonky glass, and why that “flowing glass” story is about as solid as a chocolate teapot.
Ever walked through a historic district and noticed those trippy, wavy windows? You know, the ones that make the outside world look like it’s having a mild earthquake?
If you’ve been on any historic home tours, you’ve probably heard the same story: “Glass is actually a liquid, and over hundreds of years, it’s slowly flowed downward, creating these waves.”
That, in a nutshell, is the drunken window theory. Hate to break it to you, but that’s about as accurate as claiming your house is haunted because the TV turns on by itself. (Spoiler: it’s probably just your cat sitting on the remote.)
The Truth About Your Tipsy Windows
According to Dr. Edgar Zanotto of the Federal University of São Carlos, who published the definitive paper “Do Cathedral Glasses Flow?” in the American Journal of Physics, it would take longer than the age of the universe for glass to flow noticeably at room temperature. We’re talking about 10³² years — way longer than your mortgage term.
The real story? It’s all about manufacturing, baby. In the industry we call this kind of glass “wavy glass” and it’s pretty dang cool.
Crown Glass (pre-1850): The Original Vinyl
- Glassmakers would spin molten glass into a flat disc like a glass DJ
- Created signature bullseye patterns
- Fun fact: The best pieces came from the middle, which is why being “upper crust” meant you were fancy (the outer edges were literally the upper crust of the glass)
Cylinder Glass (1850-1900): The Rolling Revolution
Scientists at the Corning Museum of Glass have documented how glassmakers would:
- Blow a massive glass bubble (like the world’s most dangerous chewing gum)
- Swing it like a pendulum to make it longer
- Cut off the ends
- Slice it down the middle
- Flatten it out (presumably while crossing their fingers)
Modern Float Glass (post-1950): The Smooth Operator
Invented by Sir Alastair Pilkington (no relation to the window company… just kidding, totally related), this process involves floating molten glass on liquid tin. It’s like a glass waterbed, but considerably more expensive.
Why Should You Care? (Besides Winning Bar Bets)
According to architectural historian David Stavros, those wavy imperfections are actually your home’s fingerprints. Each manufacturing period left distinct patterns that preservationists use to date historic buildings:
- Crown glass: Look for subtle circular patterns and occasional bullseyes
- Cylinder glass: Watch for parallel waves and elongated bubbles
- Early machine-drawn glass: Subtle horizontal ripples
- Modern float glass: Boring perfection
The National Trust for Historic Preservation notes that original windows can increase a historic home’s value by 5-15%. That’s right — those drunk-looking windows might actually be your home’s retirement plan.
Why are they more valuable? Because wavy glass isn’t being made anymore other than a few pricey niche suppliers. That makes wavy glass rare, and rare things are valuable.
A couple suppliers that make wavy glass today are below:
The Bottom Line
Have we officially busted the drunken window theory? I think so! Your old windows aren’t slowly melting like a Salvador Dalí painting. They’re more like vintage vinyl records — complete with their own imperfections that make them worth more, not less.
Sources & Further Reading:
- Zanotto, E.D. “Do cathedral glasses flow?” American Journal of Physics 66.5 (1998): 392-395. [DOI: https://doi.org/10.1119/1.19026]
- National Park Service. “The Repair and Thermal Upgrading of Historic Steel Windows.” Preservation Brief 13. [https://www.nps.gov/tps/how-to-preserve/briefs/13-steel-windows.htm]
- English Heritage. “Traditional Windows: Their Care, Repair and Upgrading.” [https://historicengland.org.uk/images-books/publications/traditional-windows-care-repair-upgrading/]
- The Window Preservation Alliance. “Historic Window Resources.” [https://windowpreservationalliance.org/resources]
Founder & Editor-in-Chief
I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.