by Bob Beranek
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Every now and then, I get on the™/AGRR™ magazine forum and read the comments and solutions given to technicians concerning the everyday problems they encounter. I must say that many on the forum are unselfish, competent professionals. I would love to meet some of you over a beer to discuss the hints and tricks of automotive glass installation because I am confident that I would learn a lot.

BobThursday06252015This weekend I read a request from an Australian reader wanting to know what we here in America use for a mirror pad adhesive. One contributor responded that he uses the ever popular Loctite mirror adhesive. The poster added that he couldn’t remember the last time he had to reattach a mirror pad. Pad technology has made strides in the way mirrors are attached to the glass surface. Mirrors rarely fall off any more, mainly due to the introduction of this new type of adhesive.

The older mirror pads were attached to the windshield with a small amount of the poly-vinyl butyral (PVB), which is used for the windshield’s lamination. The problem is that with the introduction of heat from the sun, the glass would expand and contract so often that the PVB would eventually separate from the glass. The use of Loctite mirror adhesive works great to permanently attach the pad back to the glass surface because it is an anaerobic adhesive. It will not separate due to contraction and expansion.

However, about the same time as the new adhesive for mirror pads was introduced, so were mirror pad frits. This black paint dot applied to the number four surface of the glass posed another problem many do not realize. If an anaerobic adhesive is used to attach a mirror pad to a mirror frit, it can cause a stress break emanating from the center of the mirror pad. This is caused by the restriction of free expansion and contraction of the glass. Both the glass and the adhesive must be allowed to breathe or a stress break can occur.BobThursday206252015

Glass breathes when there is a change in temperature. Transparent glass has less movement than glass with a frit applied to it. Black paint absorbs more of the heat energy found in light. The glass breathes more easily on the edges and at the mirror pad where the black frit is applied. The adhesive you use must be allowed to move with it. If it is restricted, the result is a stress break.

Loctite mirror glue or an anaerobic adhesive works well when the glass is transparent and permanent adhesion is the goal. However, I would suggest that when the need arises to adhere a mirror pad to a mirror frit, a more flexible adhesive be used to allow for the glass to breathe. I have used an epoxy, channel bond adhesive, or another flexible fast curing adhesive to attach the pad to the frit. Any others could cause a fracture when the temperature changes drastically.

Did you ever complete an installation and think to yourself that you just saved a life? Maybe you found a pinchweld so corroded that it was undermining the bead. Maybe you found glass separated from the urethane with no adhesion at all.

You could have been called out on a leak to find that the OE glass was not adhering to the adhesive and just pushed out with your hands. Perhaps the OE adhesive peeled away from the pinchweld when you began to prep the existing bead and you noticed that the paint completely failed.

My training class last week had one of those experiences. We were working on a relatively new Ford Econoline van DW1767. The glass was original equipment. We wired out the glass to demonstrate the proper use of the tool and to save the moulding. Once we got the glass out, we noticed that the urethane bead was applied very high on the pinchweld. As a matter of fact, it was more on the wall of the upper pinchweld than the floor of the pinchweld. The urethane bead was barely touching the glass at all. It was bonded to the underside of the moulding more than it was touching the bonding edge of the glass surface. The pinchweld floor had no primer or any urethane at all. It looked completely clean.

A few of my students have some experience as technicians and indicated they have seen this before on Ford Econolines. This surprised me. If it is true that this is a common problem with this vehicle, it should be announced in a loud voice to everyone who will listen. This is a problem that must be made public for the safety of all concerned.

The ANSI/AGSC/AGRSS™ Standard 003-2015 does not address the original vehicle assembly itself. The Standard does address the products used and introduced in the replacement of automotive glass, but it does not mention the defects witnessed by the technician on the vehicle itself. In 8.5 of the AGRSS™ Standard it says:

8.5 Notification of defective product:

  • A failure or defect in any product used or intended for use in the automotive glass replacement process that could jeopardize customer safety shall be reported promptly to the manufacturer or supplier of the product.


  • Any product installed by those engaged in automotive glass replacements that is discovered to be defective or which is determined could jeopardize customer safety must be immediately reported to the customer with an offer to remedy the situation.

The AGRSS™ Standard makes us responsible for the use of proper products to replace the automotive glass and for reporting defects of those products. We are also responsible for fixing bonding problems when we come upon them. However, how many Ford Econolines, without broken glass, are being driven around right now with a windshield that is inadequately bonded to the body?

As an industry, we need a mechanism to report a questionable bonding issue to the carmaker. We sometimes discuss it between ourselves and post it on™ but we need to make a greater effort to get these issues out in the open so we can force change in manufacture and make adjustments in our installations that are proven safe and effective.

The old saying, “the squeaky wheel gets the grease” is true. We need to squeak very loudly to be heard. Someone’s life may depend on it.

It is June again and with the coming of summer it is time to make adjustments to our installation process. The summer season brings warmer temperatures and higher humidity, which means faster curing times for our urethane adhesives. Is this a good thing? Faster cure times means faster safe-drive-away times, right? Yes it does, but it also means a shorter working time during the application and setting of the glass.

I remember how I learned the hard way about “tack-free time,” “skin-over time” or working time. I was doing a DW763, a General Motors full-size van back when I was a rookie. It was 90°F and 80 percent humidity and I applied the urethane before I realized I forgot to prep the glass. I quickly cleaned and primed the glass. I allowed it to dry. Just before I was going to set the glass, I checked the urethane bead and found it to be already tack free (the urethane was no longer pasty). The amount of time I had spent cleaning, priming and waiting for the dry time to pass was a short 11 minutes. The product’s printed “tack-free time” was written on the technical data sheet as 30 minutes. I should have had plenty of time to set the glass, right?

What I didn’t notice until too late was the small print at the bottom of the page: “Tack-free time 30 minutes after application at 72°F (22°C) and 50 percent relative humidity.” Of course, at a higher temperature (and higher humidity), tack-free time was considerably shorter.

This was a lesson I did not soon forget. Trying to scrape up two and a half tubes of not fully cured urethane on a hot sticky day never will be my idea of a good time.

When temperature and humidity values rise, working time decreases, sometimes dramatically. Remember that as soon as the urethane is opened, the product begins to cure. A technician should not dawdle when applying, paddling and setting the glass. In fact, any procedure that can be done before the urethane tube is opened should be completed. At the very least the glass should be clean, primed and ready to go. Then apply, paddle and set the glass without delay. Remember that warm air has the ability to hold more moisture, thus your curing times and working times are shortened in relation to the increase in temperature and humidity.

By the way, here is a little hint if you use the aluminum tubes of urethane. If you run into the situation I described above and you have to remove a partially cured bead of urethane from the pinchweld, use the other end of an emptied tube as a scooping tool. Push the tube along the pinchweld and scoop up the bead. If you oval the tube slightly, it makes for a smooth surface to re-apply the new bead. It works slick with little to no mess. Stay cool out in the field this summer.