by Bob Beranek

I belong to several glass related technicians’ groups on Facebook and enjoy participating in discussions when I can. This past week a conversation brought back memories of my installer past and the old DW837/836 windshield. I thought I would share it with my readers this week.

The DW837/836 windshield is the windshield for a 1975-1991 Ford full-sized van. Back in the day, we used to do a LOT of them. That was our service vehicle when I was an installer. It has four-sided heavy chrome mouldings and a block size of 34×73, which makes it a large and awkward piece of glass to set by yourself. The original equipment adhesive was butyl tape.

Photo Courtesy of Purple Wave

When I did these windshields, we used round butyl to replace them. I would smear some liquid butyl on the passenger side bottom pinchweld and apply the butyl tape to the glass. Then, I set the glass onto the liquid butyl, slid it to the far pinchweld, set it in place, decked it and then back sealed the seam with a flow-grade sealant. This was a successful method because we rarely had a leak or noise complaint. The two types of butyl meshed together and sealed permanently.

Our Industry Standard says:

8.4 Whenever OEM retention systems are modified on later production models without body style modification, the most current retention system shall be used in the replacement unless otherwise specified by the OEM.

However, the Ford van never had a change to urethane until the body style changed in 1992.  Thus, the OEM specifies butyl for a Ford Van of that body style so by rights, butyl could be used.

Today our industry recommends the use of urethane when replacing these parts, rather than continuing to use inferior bonding adhesives. This is to ensure the bonding is improved and not hindered and so the replacement must be done correctly.

One of the biggest challenges for field techs is that urethane and butyl are not compatible for bonding purposes. This means ALL of the butyl must be removed for proper bonding. Unfortunately butyl tape is difficult to remove, especially if the tape is older. You then must scrape off the biggest share, and continue with one of the following to remove the rest without damaging the paint:

  • Use a sharpened plastic stick to scrape off the remainder of the tape.
  • Use a big ball of old butyl to stick to the remaining butyl and peal it off.
  • Use a solvent for removal. This would require an additional process to neutralize the solvent.

In any case, it’s time consuming and difficult to accomplish.

In a past posting I suggested the use of a tool used by collision centers to remove decals and pinstriping, called an eraser. It’s a rubber wheel inserted into a drill and used as a butyl eraser; it works well. It literally erases the butyl like pencil markings from paper without damage to the paint. The tech then dusts the pinchweld of rubberized residue, primes the pinchweld, applies the urethane to the proper height and width and sets the glass using the modern setting tools or a helper.  

This method of butyl removal is fast, easy, economical and damage free. If you give it a try you won’t be sorry.

A few years ago, I was asked to judge an auto glass installation competition at a large western glass company. That company planned on having the competition at a race track in their area so spectators would be able to watch. The temperature that day was going to exceed 100°F and the vehicles were parked outside in full sunlight.

When the judges arrived, we checked the adhesive instructions which stated that the application temperature should not exceed 110°F. Obviously, we were concerned about the high temperatures surrounding the competition. However, when the instructions said “application temperature” did they mean product temperature, surface temperature or ambient temperature?  What would be the ramifications of applying the adhesive in extreme temperatures?

We had an adhesive representative who was present for the competition, so we asked him for advice. Unfortunately, he did not know the exact answer, and due to the fact that the competition was occurring on a weekend, we were unable to contact a technical advisor at the adhesive company’s technical lab.

Through some serious discussion between the replacement company owner, the adhesive representative and the judges, we decided to take steps to cool down everything involved with the installation. We placed the glass and adhesives into air-conditioned service vehicles to make sure that the glass surface and the adhesives were well under the temperature limit of 110°F. We also started the vehicles and ran the air-conditioning in advance of the competition to assure that the vehicle was cooled down before the competition proceeded. We weren’t sure at the time what the upper temperature limit of the “Application Temperature” meant, but we were certainly not going to install glass under conditions contraindicated by the sealant manufacturers.

Since that incident occurred, I have researched this issue and found that there are different consequences for applying adhesives beyond their temperature limits. They can include bonding deficiencies, application problems and storage concerns. Obviously, the most important of these consequences is the bonding problem. If the sealant does not bond properly, the result could be injury or death caused by improper glass performance in a crash.

If the adhesive loses its viscosity, the adhesive pre-maturely cures, and waste is the obvious result. If the adhesive loses its thickness due to higher than normal temperatures, it can drip onto the customer’s interior causing vehicle damage. Under extreme heat conditions, the weight of the glass can flatten the windshield to the pinchweld’s metal and cause a stress fracture. Lastly, if sealants are stored improperly, the product cannot be expected to be to perform as promised.

The moral of the story and the research we conducted says one thing, temperature matters and caution must be exercised to insure proper performance of your adhesive products. Check your adhesive’s technical data and installation instructions for temperature limitations.  If for some reason the data is missing or not clear, check with your adhesive rep. If the rep is unsure, check with the adhesive company’s technical expert for clarity. This is important. It is not enough to go through the procedures perfectly if you don’t know your products limitations. Do it right every time and think before you proceed.