Jeff Gage wrote in response to my last post:

“Great topic, in light of this information, when is NAGS going to publish…a definitive measurement of urethane application? … What exactly is the definition of a kit? Is a “kit” simply the urethane, primers, and dam as listed by NAGS, or is it to include the tape, solvents, and other peripherals required to insure that the job is done correctly?” 

I thought that this comment and the attached questions are good enough to address them in detail.

What is a “kit” anyway?

A kit is defined as the supplies necessary to install a stationary auto glass part into a vehicle.  Most auto glass professionals think that it is the urethane and it’s supporting materials but actually it is all of the materials and supplies needed to install the glass except the approved add-ons of moldings and/or clips. These kit supplies can be paper towels, razor blades, solvents, cleaners, daubers, tapes, and any other items used during and after the installation.  This is a little disconcerting considering that many of the approved “kit” allowances are less than the cost of the needed urethane for that vehicle let alone the other items and supplies listed in the “kit.”

Jeff also asked, “…when is NAGS going to publish …a definitive measurement of urethane application.”  Jeff asks another good question but one that I can only speculate on. NAGS will have to answer this one because they only know why they do the things they do and print the things they print. However, I think they don’t publish definitive measurement because they don’t know the actual volume measurement.

Service manuals, printed by the vehicle manufacturers, list the specifications and configuration of the bead but do not print the amount used. I suspect that a good mathematician can calculate the exact volume of urethane used but it seems that the manufacturers don’t think it is important enough to publish. NAGS publishes the estimate because it is important to retailing glass shops for billing purposes.

So what should we do? We should replicate the dimensions as close as we can to the OE and communicate the true volume to NAGS so they can accurately report the amount used.

So how do we replicate the OE bead? I do address my method of estimating the bead size and configuration in my training courses and in my book, “The Complete Guide to Auto Glass Installation-A Textbook,” in great detail – get the gratuitous plug for my book?—but here is a brief synopsis.

  1. Once the bead is trimmed back, find the thinnest representation of the OE bead. We pick the thinnest because it is the bead programmed in the computer for the robot to follow. The reason for the different thicknesses is the various pressures put upon the windshield during vehicle assembly while the urethane is still uncured.
  2. Take the tip of the urethane tube and cut the tip to the proper width. Use the inside diameter of the tip as a measure and cut the tip straight across and not at a 45º angle. The 45º angle lays the urethane bead on the bonding surface and does not apply the bead to the bonding surface.  Laying the bead can bridge a gap and cause bonding and leak problems.
  3. Cut a “V” notch equal to or higher than the wall of the upper “L” shaped pinchweld.  This assures that the underside of the glass will make contact with the urethane before the glass is push down into its final position.

Note: If the vehicle has clipped moldings, then the “V” bead should be equal to or higher than the height of the clips and not the wall of the pinchweld. Then use the moldings to push the glass downward until the clips engage. This assures a good tight fit of the moldings to the glass surface.

Jeff—I hope this answers your questions.

To all of my other readers, I hope this gives you some reasons to rethink your urethane application habits and follow the methods that have proven successful.