I remember one of the first training classes I conducted for the National Glass Association’s Auto Glass Technical Institute in Arizona in the early 1990s. For the hands-on component of the school we used vehicles with broken glass that students and teachers donated for training. It was a big class and we scheduled 17 windshields for replacement. I was shocked to see that 13 out of the 17 vehicles had prior installations done with butyl tape over urethane. I was so surprised by this that I actually thought it was an anomaly that I would never see again.
Well, I was wrong. The next month we did a class in Orange County, Calif. There, 10 out of 15 vehicles had incorrectly bonded windshields, mostly butyl over urethane, although one was sealed with a material that I could not identify. This was a real shock for a Midwestern installer. I actually believed that most techs used the right materials. They may not be using them correctly, but I thought they at least tried to install it correctly.
That is when I realized that many, if not most, auto glass technicians had no idea of the proper procedures for installing auto glass. They received on-the-job training from people who did not know what they were doing. I must say that those two experiences did reinforce my career choice, but it was sad at the same time.
Even today, no matter where you install auto glass, there will be times that you will come across a windshield or other glass part that was previously bonded improperly with an unknown adhesive. In these cases, the adhesive present must be completely removed and replaced with the proper urethane adhesive, even if it means using solvent application, media blast (sand blasting) or an abrasive media to remove it. Any foreign material left behind could cause an improper seal and the possibly of a liability claim in the future.
If solvent is needed to remove foreign material, the solvent itself has to be removed before the urethane can be applied. The procedure for removing solvent residue was discussed in past postings but here it is again for reference:
- Remove the foreign material with an application of solvent.
- Spray the surface cleaned with a generous amount of approved glass cleaner.
- Rub the glass cleaner in with your fingertips. The oils in your hands mix the cleaner and solvent and ease the removal of solvent residue.
- Repeat if necessary.
- Add liberal amounts of water to the surface to wash off the glass cleaner residue.
- Repeat as often as necessary until the surface is free of any contaminants.
If a media blast or abrasive grinding is required, remove only the foreign material and not the paint or e-coat layers. Look for a tool the collision centers use to remove decals and other films from a painted surface called a graphics remover eraser. It feels like the material a pencil eraser is made from. It literally erases the butyl from the pinchweld without damage to the paint. However, if bare metal is exposed, use the bare metal preparation steps outlined by your adhesive manufacturer. Another method is using butyl against itself. A big ball of butyl stuck to the butyl on the pinchweld peels off the old butyl and leaves the pinchweld clean with little damage.
Don’t forget, the Auto Glass Replacement Safety (AGRSS®) Standard requires that improper prior installations must be corrected and restored to OE installation requirements. Don’t put your customers in danger. Complete the installation correctly every time. It will pay off; trust me.