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Where has all the Butyl Tape gone?

This 1970 El Camino had a ‘tape in’ windshield using Butyl tape

Many of our customers who are in the midst of a restoration reach out to us with questions about butyl tape. Sometimes the vehicle they are restoring used butyl tape originally or it's been recommended by others to set their windshield. To their surprise, even with the large quantity of glass gaskets we offer, butyl tape is not something we carry, and there's a reason for that.

Originally, auto manufacturers installed the windshield and rear window glass with a rubber gasket. That took a lot of time on the assembly line, so in the mid 60’s, General Motors switched to butyl tape. This sped up the process and worked well enough that other auto manufacturers soon followed suit.

In the mid 60’s, cars started changing from having a body over a frame to unibody style construction (where the body also served as the frame of the vehicle, with added support around the engine, of course). Unibody construction made rigidity more important than ever and while butyl tape was really great at sealing, it offered little strength. As vehicles shifted to a unibody frame construction, the windshield and rear window had to possess strength as they became integral parts of the vehicle's structure. So, a more effective method of attaching them was required.

Graphic of differences between body over frame and unibody vehiclesBody over frame vs. unibody

During this time period, adhesive technology made major improvements and urethane adhesive became the better choice. It offers excellent sealing and strength all while still providing some flexibility/movement. The 3M website says: “Urethane structural adhesives are two-part formulations that react when mixed and do not require moisture to cure. They are relatively flexible when cured and therefore tend to have excellent impact and vibration resistance” making it perfect for this application.

In the mid 70’s, the gradual switch to urethane adhesive for bonded windshields and rear windows began, and was standard operating procedure by the 80's.

Photo of 3M urethane adhesive
3M Urethane Adhesive

Butyl tape is still out there on the market (it’s used for many things), but we always recommend urethane adhesive for this application. We carry the 3M Brand, but you can also purchase it at any local auto parts store. It comes in a caulk style tube for easy application and typically cures in 24 hours.

To set your windshield or rear window with it, simply run a bead on the edge the glass sits on, push the glass down on it and leave it to cure. You’ll also want to use spacers to get the glass lined up just right and hold it in place until the adhesive cures.

Urethane adhesive can also be used to attach universal beltline or beltline weatherstrip without tabs. Simply run a bead on the gluing surface, push the beltline on and use some wooden clothespins or wood clamps to hold it in place. Remove the clamps after 24 hours and you’ll be ready to go!

We demonstrate how to attach Beltline Weatherstripping using Urethane Adhesive

Steele not only has all the products you need but all the knowledge you need to get the job done right, too. If you have questions about Rubber Parts or Weatherstripping on your Classic Car, Truck, Hot Rod or even your boat, trailer or RV, feel free to reach out to us! You can call us at 800-650-4482 or contact us through our website. Check out our YouTube channel for our full library of how-to/installation videos.