What Is Isinglass Clear Window Material?

Item # X-HT-300400

The Hazy History of Isinglass

Isinglass is an outdated, somewhat generic term for clear window material. It's also spelled “eisenglass” (which translates to “iron glass” in German) and “isenglass.” Isinglass is a form of mica, which are any of various opaque or transparent minerals made from watery silicates of aluminum or potassium. Mica is mined all over the world, and these minerals are crystallized into shapes that can be cut into very thin, transparent sheets. Thus it was used in the early production of clear window material found in carriages, automobiles and street lanterns throughout the 19th and early 20th centuries.

What Is Isinglass Clear Window Material 3Early automobiles like this Ford Model T used isinglass in the side windows. These windows could be removed or rolled up during nice weather. Photo courtesy of the Walter J. Hussey Collection at the National Museum of American History.

Perhaps one of the reasons isinglass has solidified itself as a term for clear window material is, in part, thanks to a famous American musical. In Rogers and Hammerstein’s 1943 hit “Oklahoma!,” the song “The Surrey With the Fringe on Top” has a line — in describing the surrey — that goes: “The upholstery’s brown, the dashboard’s genuine leather. With i sin-glass curtains y’can roll right down, in case there’s a change in the weather.” The name stuck — even though real isinglass has nothing to do with the manufacture of today’s synthetic window vinyl — and has been used ever since as a synonym for flexible clear window material that can be rolled up.

The confusion surrounding the word also comes from the fact that isinglass is semitransparent gelatin found in the air bladders of fish, particularly sturgeons, hake and cod. This isinglass is harvested and processed for a variety of uses. It was used throughout the 19th and 20th centuries in the manufacture of glue and cement. It’s still used today as a clarifying agent in jellies, wine and beer. The isinglass prepared from fish bladders has nothing to do with transparent window material; they just share a name.

Today’s Boat Window Material

As previously stated, isinglass was never a brand of window material. It was a mineral product commonly used in everything from carriages and street lamps to early automobile windows and boat curtains. Thin, transparent sheets of isinglass (aka mica) were used in boilers, lanterns and stoves — then later as lampshades with the discovery of electricity — because mica is heat resistant and less likely to shatter than glass. Its use soared during the 1800s and 1900s but has since been replaced by more durable and higher quality synthetic vinyl materials.

Today, brands like Strataglass™, Regalite®, Crystal Clear and O’Sea® are the new favorites in the vinyl window industry. Unlike isinglass, these brands are press-polished, which is a manufacturing method of taking two layers of material and pressing them together between highly polished chrome plates. This process produces one thicker polished sheet of the most optically and consistently clear window vinyl. Outdated isinglass material was at risk of yellowing, hazing, peeling and turning brittle over time. The brands of window material we carry at Sailrite are the best in the industry and will hold up to years of use while retaining exceptional optical clarity and durability.

Here’s a quick rundown of the vinyl window brands we carry, their qualities and specifications:

Strataglass: This press-polished window material has a VueShield™ protective, scratch-resistant coating. Available in 30-, 40- and 60-gauge thicknesses. 40-gauge comes in Clear and Light Smoke. Cold Crack Rating of -10 degrees Fahrenheit.

O’Sea: This polyvinyl chloride, press-polished window material is chemically resistant to suntan lotion, insect repellent and jet fuel vapor. It has a slightly bluish tint. Available in 30- and 40-gauge thicknesses in Clear only. Cold Crack Rating of -30 degrees Fahrenheit.

Regalite: A standard polyvinyl chloride marine grade window material in a flexible, press-polished sheet without the superior chemical resistance that O’Sea has. Available in 20-, 30- and 40-gauge thicknesses in Clear only. Cold Crack Rating of -30 degrees Fahrenheit.

Crystal Clear: This press-polished window material is made using the same materials and manufacturing as Strataglass, but it does not have the VueShield protective coating. Available in 20-, 30- and 40-gauge thicknesses. 40-gauge comes in Clear and Light Smoke. Cold Crack Rating of -10 degrees Fahrenheit.

What Is Isinglass Clear Window Material 4We used Strataglass for this dodger windshield that can be rolled up to let in a refreshing breeze.

The key to keeping your vinyl windows looking and performing their best is by maintaining the quality of the material with regular cleaning and maintenance. All vinyl window material — regardless of brand — contains plasticizers that will break down over time and cause your windows to turn hazy and brittle. To protect the integrity of your windows, you need to apply protective products like 303® UV Aerospace Protectant or IMAR™ to keep your windows looking like new longer. With regular application, these products will extend the life of your vinyl windows.

Want to learn even more about the clear window vinyls we offer? Check out our blog “Choosing a Clear Vinyl Window Material” (200558XHT) to read about window material terms you need to know when shopping for your next window project. We also have a “Window Material Buying Guide” (300087XHT) downloadable chart to help you compare the various window material brands we carry. As always, if you have any additional questions about which vinyl window material is right for your application, feel free to email or call us. We’re happy to help!





The Smithsonian Institute Digital Archive www.si.edu